fix: runestone formula, prestige/transcendence rebalance, exploration fixes, and comprehensive balance audit (#135)

## What changed and why

### Runestone formula (`prestige.ts`)
- Swapped `sqrt` for `cbrt` — much stronger diminishing returns for large gold values
- Added base cap of **200** (→ ~1,125 max with all upgrades at 5.625× multiplier)
- Prevents extended AFK sessions from producing runestone windfalls that allow immediate upgrade purchasing and rapid prestige chaining

### Prestige threshold formula (`prestige.ts`)
- Old: `1,000,000 × 5^n` — exponential, grows impossibly fast, prestige 10+ takes years
- New: `1,000,000 × (n+1)²` — polynomial, peaks at ~1 day/run around P8–10, then gets *easier* as the production multiplier overtakes it
- Removed `thresholdScaleFactor` constant (no longer needed)

### Production multiplier (`prestige.ts`)
- Old: `1.15^n`
- New: `1.25^n` — compounds faster, ensures the polynomial threshold eventually gets easy in the late game

### Boss prestige requirements (`bosses.ts`)
- Rescaled proportionally from 0–88 range to 0–20 range
- The Absolute One now requires prestige **20** (was 88), making transcendence reachable in a few weeks of idle play

### Echo formula (`transcendence.ts`)
- Constant changed from 853 → **224**
- At the target prestige of 20: `floor(224 / sqrt(20)) = 50 echoes` per transcendence (no meta upgrades)
- With all echo_meta upgrades (3.75× total): up to **187 echoes** per transcendence

### Transcendence upgrade costs (`transcendenceUpgrades.ts`)
- Old total: **866 echoes** → New total: **400 echoes** (roughly halved across all categories)
- Apotheosis still requires **all 15 upgrades** purchased

### Balance fixes (closes #141, #142, #143, #144, #145)
- Equipment: `philosophers_stone` click multiplier 2.25→2.5, `crystal_shard` 1.55→1.65 (#144)
- Recipes: added `primal_omega_lens` cross-zone click_power recipe at 1.38× (#142)
- Adventurers: `celestial_guard` base cost adjusted to smooth tier 14→15→16 cost curve (#145)

### Quest reward rebalancing (closes #136, #137)
- Shadow Marshes: buffed `shadow_mere`, `witch_coven`, `plague_ruins` rewards to match combat requirements (#136)
- Astral Void: added gold to `void_rift`, increased rewards across all Astral Void quests (#137)

### Boss reward additions (closes #138, #139, #140)
- Assigned 9 unassigned adventurer-specific upgrades to Crystalline Spire through Eternal Throne bosses that had empty `upgradeRewards` arrays (#140)

### Combat power documentation (closes #153)
- Expanded JSDoc on `computePartyCombatPower` to clarify companion `bossDamage` multiplier behaviour

### Effective adventurer stats (closes #154)
- Added `computeEffectiveAdventurerStats` to `tick.ts` and updated `AdventurerCard` to display effective post-multiplier stats

### Adventurer upgrade timing (closes #158)
- Audited every adventurer-specific upgrade reward — upgrades now land within the same progression window where that adventurer tier is still a meaningful contributor

### Sync and save fixes (closes #147, #148, #151)
- Fixed sync new content count to report only genuinely changed items (#147)
- Fixed signature mismatch after first auto-boss completion (#148)
- Added auto-buy cap (100) on non-max-tier adventurers (#151)

### Auto-adventurer persistence (closes #156)
- Auto-buy preference now preserved across prestige resets

### Broken CDN image (closes #159)
- Uploaded missing `auto_adventurer.jpg` to CDN

### Codex unlock hints (closes #146)
- Locked codex entries now display a hint generated from `sourceType` and `sourceId`

### Exploration bug fixes (closes #160, #161)
- Fixed auto-save race condition discarding exploration materials collected mid-tick (#160)
- Fixed exploration areas failing to unlock when zone was unlocked via boss kill or quest completion (#161)

### Concurrent prestige fix (closes #162)
- Added optimistic locking via `updatedAt` — concurrent prestige requests return 409

### Prestige UX (closes #163)
- Added `reloadSilent` to game context — no loading screen flash after prestige

### Balance adjustments (closes #164, #165, #166, #167)
- Reduced `shadow_mere` CP requirement 5,000,000 → 2,000,000 (#164)
- Buffed crystal drops from Shadow Marshes bosses and quests (#165)
- Increased runestone yield from 10 → 15 per prestige level (#166)
- Daily challenge set always includes a clicks challenge (#167)

### Progression QoL (closes #168, #169)
- Added `computeProjectedRunestones()` and persistent `+N On Prestige` resource bar row (#168)
- Added `enablePrestigeAnnouncements` setting per player (#169)

---

## Comprehensive balance audit (closes #187, #191, #192, #193, #194, #195, #196, #197, #198)

### Crystal economy fixes
- Zeroed crystal rewards for all Zone 7+ boss drops (Celestial Reaches onwards) — crystals are an early/mid-game currency and should not flow freely into the endgame (#187)
- Zeroed crystal rewards for all Zone 9+ quest rewards (Infernal Court onwards) — same rationale (#191)

### Achievement additions and fixes
- Added quest milestone achievements at 75 quests (10,000 crystals) and 100 quests (15,000 crystals)
- Added boss milestone achievement at 50 bosses (15,000 crystals)
- Added prestige milestone achievements at P50, P100, P150, P200 — rewarding **runestones** rather than crystals to match the late-game economy
- Added gold milestone achievements through 1e90 gold earned
- Fixed `quest_eternal` condition from 122 → **112** (actual quest count) — was permanently impossible (#197)
- Fixed `fully_equipped` condition from 65 → **78** (actual equipment count after new items) (#197)
- Fixed `devourer_slayer` description to remove incorrect zone reference

### Upgrade balance
- Fixed Essence Guild multiplier 1.5× → **2×** — was identical to the cheaper Merchant Alliance for 5× the cost (#194)
- Raised Void Ascendancy crystal cost 10M → **50M** — was trivially cheap compared to the parallel Celestial Mandate upgrade (100B essence + 50T gold) (#195)
- Fixed Sunken Temple quest rewards (gold 2M → 60M, essence 1,500 → 25,000, crystals 75 → 400) — was rewarding less than its easier prerequisite Witch Coven (#193)

### Equipment balance
- Buffed Eternal Prism stats to click 5×, combat **3×**, gold **2.5×** — was only marginally better than the free Eternity Stone boss drop for 100M crystals (#196)

### Missing content
- Created **13 missing equipment items** for Zones 15–18 (primordial_chaos through the_absolute) that were referenced by late-game boss `equipmentRewards` arrays but never existed in `equipment.ts` (#198):
  - `chaos_mantle`, `titan_core` (Primordial Chaos)
  - `expanse_blade`, `void_armour_mk2` (Infinite Expanse)
  - `cosmos_blade`, `reality_plate` (Reality Forge)
  - `maelstrom_edge`, `cosmic_plate` (Cosmic Maelstrom)
  - `primeval_blade`, `ancient_aegis` (Primeval Sanctum)
  - `absolute_blade`, `eternity_plate`, `omniversal_core` (The Absolute)
- Stats scale from combat 14× / gold 9× (Zone 15) up to combat 28× / gold 20× for the final boss drops

### Type system
- Extended `AchievementReward` type to support `runestones` field
- Updated tick engine achievement processing to award both crystals and runestones

---

## Target progression timeline (optimal play, ~16h/day idle)
- First cycle to P20: ~375h (~3.3 weeks)
- Each subsequent cycle gets faster as echo upgrades boost income/combat/threshold
- Expected **~5 transcendences** before apotheosis at 50–187 echoes/transcendence
- **~6 months** to apotheosis for a dedicated player

## Test plan
- [ ] Lint, build, and test pipeline passes (100% coverage maintained)
- [ ] Prestige threshold at P0 is still 1,000,000 gold
- [ ] Prestige runs feel ~1 day long around P8–10 and get easier after
- [ ] The Absolute One is locked until prestige 20
- [ ] Transcendence at P20 awards 50 echoes (no meta upgrades)
- [ ] All 15 transcendence upgrades cost 400 echoes total
- [ ] Bosses in Zones 7+ drop 0 crystals; Zones 1–6 retain crystal drops
- [ ] Quests in Zones 9+ reward 0 crystals; Zones 1–8 retain crystal rewards
- [ ] Sunken Temple rewards more gold/essence/crystals than Witch Coven
- [ ] Essence Guild gives 2× income (stronger than Merchant Alliance 1.5×)
- [ ] Void Ascendancy costs 50M crystals
- [ ] Eternal Prism stats are click 5×, combat 3×, gold 2.5×
- [ ] Late-game bosses (primordial_titan through the_absolute_one) drop equipment on kill
- [ ] `quest_eternal` achievement requires 112 quests
- [ ] `fully_equipped` achievement requires 78 equipment pieces
- [ ] P50/P100/P150/P200 prestige achievements reward runestones
- [ ] Adventurer cards show effective post-multiplier stats
- [ ] Exploration areas unlock correctly when their zone is unlocked
- [ ] Concurrent prestige requests return 409
- [ ] No loading screen flash after prestige
- [ ] Daily challenge set always includes a clicks challenge
- [ ] Resource bar shows `+N On Prestige` runestone preview

✨ This PR was crafted with help from Hikari~ 🌸

Reviewed-on: #135
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/api/src/routes/debug.ts

@@ -642,6 +642,14 @@ const patchAdventurerStats = (state: GameState): number => {
     if (defaultAdventurer === undefined) {
       continue;
     }
+    const hasChanged
+      = savedAdventurer.baseCost !== defaultAdventurer.baseCost
+      || savedAdventurer.class !== defaultAdventurer.class
+      || savedAdventurer.combatPower !== defaultAdventurer.combatPower
+      || savedAdventurer.essencePerSecond !== defaultAdventurer.essencePerSecond
+      || savedAdventurer.goldPerSecond !== defaultAdventurer.goldPerSecond
+      || savedAdventurer.level !== defaultAdventurer.level
+      || savedAdventurer.name !== defaultAdventurer.name;
     savedAdventurer.baseCost = defaultAdventurer.baseCost;
     savedAdventurer.class = defaultAdventurer.class;
     savedAdventurer.combatPower = defaultAdventurer.combatPower;
@@ -649,7 +657,9 @@ const patchAdventurerStats = (state: GameState): number => {
     savedAdventurer.goldPerSecond = defaultAdventurer.goldPerSecond;
     savedAdventurer.level = defaultAdventurer.level;
     savedAdventurer.name = defaultAdventurer.name;
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };
@@ -670,6 +680,15 @@ const patchQuestStats = (state: GameState): number => {
     if (defaultQuest === undefined) {
       continue;
     }
+    const savedPrereqs = JSON.stringify(savedQuest.prerequisiteIds);
+    const defaultPrereqs = JSON.stringify(defaultQuest.prerequisiteIds);
+    const hasChanged
+      = savedQuest.name !== defaultQuest.name
+      || savedQuest.description !== defaultQuest.description
+      || savedQuest.durationSeconds !== defaultQuest.durationSeconds
+      || savedPrereqs !== defaultPrereqs
+      || savedQuest.zoneId !== defaultQuest.zoneId
+      || savedQuest.combatPowerRequired !== defaultQuest.combatPowerRequired;
     savedQuest.name = defaultQuest.name;
     savedQuest.description = defaultQuest.description;
     savedQuest.durationSeconds = defaultQuest.durationSeconds;
@@ -678,7 +697,9 @@ const patchQuestStats = (state: GameState): number => {
     if (defaultQuest.combatPowerRequired !== undefined) {
       savedQuest.combatPowerRequired = defaultQuest.combatPowerRequired;
     }
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };
@@ -689,6 +710,7 @@ const patchQuestStats = (state: GameState): number => {
  * @param state - The player's current game state (mutated in place).
  * @returns The number of boss entries whose stats were updated.
  */
+/* eslint-disable-next-line complexity, max-statements -- Comparing many boss stat fields for change detection */
 const patchBossStats = (state: GameState): number => {
   const defaultBossMap = new Map(defaultBosses.map((boss) => {
     return [ boss.id, boss ] as const;
@@ -699,6 +721,20 @@ const patchBossStats = (state: GameState): number => {
     if (defaultBoss === undefined) {
       continue;
     }
+    const savedRewards = JSON.stringify(savedBoss.equipmentRewards);
+    const defaultRewards = JSON.stringify(defaultBoss.equipmentRewards);
+    const hasChanged
+      = savedBoss.name !== defaultBoss.name
+      || savedBoss.description !== defaultBoss.description
+      || savedBoss.maxHp !== defaultBoss.maxHp
+      || savedBoss.damagePerSecond !== defaultBoss.damagePerSecond
+      || savedBoss.goldReward !== defaultBoss.goldReward
+      || savedBoss.essenceReward !== defaultBoss.essenceReward
+      || savedBoss.crystalReward !== defaultBoss.crystalReward
+      || savedRewards !== defaultRewards
+      || savedBoss.prestigeRequirement !== defaultBoss.prestigeRequirement
+      || savedBoss.zoneId !== defaultBoss.zoneId
+      || savedBoss.bountyRunestones !== defaultBoss.bountyRunestones;
     savedBoss.name = defaultBoss.name;
     savedBoss.description = defaultBoss.description;
     savedBoss.maxHp = defaultBoss.maxHp;
@@ -710,7 +746,9 @@ const patchBossStats = (state: GameState): number => {
     savedBoss.prestigeRequirement = defaultBoss.prestigeRequirement;
     savedBoss.zoneId = defaultBoss.zoneId;
     savedBoss.bountyRunestones = defaultBoss.bountyRunestones;
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };
@@ -731,12 +769,20 @@ const patchZoneStats = (state: GameState): number => {
     if (defaultZone === undefined) {
       continue;
     }
+    const hasChanged
+      = savedZone.name !== defaultZone.name
+      || savedZone.description !== defaultZone.description
+      || savedZone.emoji !== defaultZone.emoji
+      || savedZone.unlockBossId !== defaultZone.unlockBossId
+      || savedZone.unlockQuestId !== defaultZone.unlockQuestId;
     savedZone.name = defaultZone.name;
     savedZone.description = defaultZone.description;
     savedZone.emoji = defaultZone.emoji;
     savedZone.unlockBossId = defaultZone.unlockBossId;
     savedZone.unlockQuestId = defaultZone.unlockQuestId;
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };
@@ -747,6 +793,7 @@ const patchZoneStats = (state: GameState): number => {
  * @param state - The player's current game state (mutated in place).
  * @returns The number of upgrade entries whose stats were updated.
  */
+/* eslint-disable-next-line complexity -- Comparing many upgrade stat fields for change detection */
 const patchUpgradeStats = (state: GameState): number => {
   const defaultUpgradeMap = new Map(defaultUpgrades.map((upgrade) => {
     return [ upgrade.id, upgrade ] as const;
@@ -757,6 +804,15 @@ const patchUpgradeStats = (state: GameState): number => {
     if (defaultUpgrade === undefined) {
       continue;
     }
+    const hasChanged
+      = savedUpgrade.name !== defaultUpgrade.name
+      || savedUpgrade.description !== defaultUpgrade.description
+      || savedUpgrade.target !== defaultUpgrade.target
+      || savedUpgrade.adventurerId !== defaultUpgrade.adventurerId
+      || savedUpgrade.multiplier !== defaultUpgrade.multiplier
+      || savedUpgrade.costGold !== defaultUpgrade.costGold
+      || savedUpgrade.costEssence !== defaultUpgrade.costEssence
+      || savedUpgrade.costCrystals !== defaultUpgrade.costCrystals;
     savedUpgrade.name = defaultUpgrade.name;
     savedUpgrade.description = defaultUpgrade.description;
     savedUpgrade.target = defaultUpgrade.target;
@@ -767,7 +823,9 @@ const patchUpgradeStats = (state: GameState): number => {
     savedUpgrade.costGold = defaultUpgrade.costGold;
     savedUpgrade.costEssence = defaultUpgrade.costEssence;
     savedUpgrade.costCrystals = defaultUpgrade.costCrystals;
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };
@@ -778,6 +836,7 @@ const patchUpgradeStats = (state: GameState): number => {
  * @param state - The player's current game state (mutated in place).
  * @returns The number of equipment entries whose stats were updated.
  */
+/* eslint-disable-next-line complexity, max-statements -- Comparing many equipment stat fields for change detection */
 const patchEquipmentStats = (state: GameState): number => {
   const defaultEquipmentMap = new Map(defaultEquipment.map((item) => {
     return [ item.id, item ] as const;
@@ -788,6 +847,18 @@ const patchEquipmentStats = (state: GameState): number => {
     if (defaultItem === undefined) {
       continue;
     }
+    const savedBonus = JSON.stringify(savedItem.bonus);
+    const defaultBonus = JSON.stringify(defaultItem.bonus);
+    const savedCost = JSON.stringify(savedItem.cost);
+    const defaultCost = JSON.stringify(defaultItem.cost);
+    const hasChanged
+      = savedItem.name !== defaultItem.name
+      || savedItem.description !== defaultItem.description
+      || savedItem.type !== defaultItem.type
+      || savedItem.rarity !== defaultItem.rarity
+      || savedBonus !== defaultBonus
+      || savedCost !== defaultCost
+      || savedItem.setId !== defaultItem.setId;
     savedItem.name = defaultItem.name;
     savedItem.description = defaultItem.description;
     savedItem.type = defaultItem.type;
@@ -799,7 +870,9 @@ const patchEquipmentStats = (state: GameState): number => {
     if (defaultItem.setId !== undefined) {
       savedItem.setId = defaultItem.setId;
     }
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };
@@ -820,6 +893,16 @@ const patchAchievementStats = (state: GameState): number => {
     if (defaultAchievement === undefined) {
       continue;
     }
+    const savedCondition = JSON.stringify(savedAchievement.condition);
+    const defaultCondition = JSON.stringify(defaultAchievement.condition);
+    const savedReward = JSON.stringify(savedAchievement.reward);
+    const defaultReward = JSON.stringify(defaultAchievement.reward);
+    const hasChanged
+      = savedAchievement.name !== defaultAchievement.name
+      || savedAchievement.description !== defaultAchievement.description
+      || savedAchievement.icon !== defaultAchievement.icon
+      || savedCondition !== defaultCondition
+      || savedReward !== defaultReward;
     savedAchievement.name = defaultAchievement.name;
     savedAchievement.description = defaultAchievement.description;
     savedAchievement.icon = defaultAchievement.icon;
@@ -827,7 +910,9 @@ const patchAchievementStats = (state: GameState): number => {
     if (defaultAchievement.reward !== undefined) {
       savedAchievement.reward = { ...defaultAchievement.reward };
     }
-    patched = patched + 1;
+    if (hasChanged) {
+      patched = patched + 1;
+    }
   }
   return patched;
 };