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/web/src/context/gameContext.tsx

@@ -53,11 +53,13 @@ import {
   transcend as transcendApi,
 } from "../api/client.js";
 import { CODEX_ENTRIES } from "../data/codex.js";
+import { EXPLORATION_AREAS } from "../data/explorations.js";
 import { RECIPES } from "../data/recipes.js";
 import {
   RESOURCE_CAP,
   applyTick,
   calculateClickPower,
+  computePartyCombatPower,
 } from "../engine/tick.js";
 import { updateChallengeProgress } from "../utils/dailyChallenges.js";
 import { formatNumber as formatNumberUtil } from "../utils/format.js";
@@ -115,6 +117,9 @@ const applyBossResult = (
         }).
         filter(Boolean),
     );
+    const newlyUnlockedZoneIds = new Set(unlockedZones.map((z) => {
+      return z.id;
+    }));
 
     const challengeUpdate
       = previous.dailyChallenges === undefined
@@ -215,6 +220,23 @@ const applyBossResult = (
           ? { ...u, unlocked: true }
           : u;
       }),
+      ...newlyUnlockedZoneIds.size === 0 || previous.exploration === undefined
+        ? {}
+        : {
+          exploration: {
+            ...previous.exploration,
+            areas: previous.exploration.areas.map((area) => {
+              const areaDefinition = EXPLORATION_AREAS.find((definition) => {
+                return definition.id === area.id;
+              });
+              return areaDefinition !== undefined
+                && newlyUnlockedZoneIds.has(areaDefinition.zoneId)
+                && area.status === "locked"
+                ? { ...area, status: "available" as const }
+                : area;
+            }),
+          },
+        },
     };
   }
 
@@ -288,6 +310,12 @@ interface GameContextValue {
    */
   reload: ()=> Promise<void>;
 
+  /**
+   * Reload state from the server without showing the loading screen (used
+   * after prestige to avoid the visible flash/hang).
+   */
+  reloadSilent: ()=> Promise<void>;
+
   /**
    * Unix timestamp of the last successful cloud save (null until first save response).
    */
@@ -696,6 +724,10 @@ export const GameProvider = ({
 
     /* No-op placeholder */
   });
+  const reloadSilentReference = useRef<()=> Promise<void>>(async() => {
+
+    /* No-op placeholder */
+  });
   const [ schemaOutdated, setSchemaOutdated ] = useState(false);
   const [ saveSchemaVersion, setSaveSchemaVersion ] = useState(0);
   const [ currentSchemaVersion, setCurrentSchemaVersion ] = useState(0);
@@ -783,6 +815,32 @@ export const GameProvider = ({
 
   reloadReference.current = reload;
 
+  const reloadSilent = useCallback(async() => {
+    setError(null);
+    try {
+      const data = await loadGame();
+      setState(data.state);
+      setLastSavedAt(data.state.player.lastSavedAt);
+      if (data.signature !== undefined) {
+        signatureReference.current = data.signature;
+        localStorage.setItem("elysium_save_signature", data.signature);
+      }
+      setLoginStreak(data.loginStreak);
+      setSchemaOutdated(data.schemaOutdated);
+      setSaveSchemaVersion(data.state.schemaVersion ?? 0);
+      setCurrentSchemaVersion(data.currentSchemaVersion);
+      setInGuild(data.inGuild);
+    } catch (error_: unknown) {
+      setError(
+        error_ instanceof Error
+          ? error_.message
+          : "Failed to load game",
+      );
+    }
+  }, []);
+
+  reloadSilentReference.current = reloadSilent;
+
   useEffect(() => {
     enableSoundsReference.current = enableSounds;
   }, [ enableSounds ]);
@@ -1078,11 +1136,7 @@ export const GameProvider = ({
             return q.status === "active";
           });
           if (!hasActiveQuest) {
-            // eslint-disable-next-line unicorn/no-array-reduce -- Need the total!
-            const partyCombatPower = next.adventurers.reduce((total, a) => {
-              const power = total + a.combatPower;
-              return power * a.count;
-            }, 0);
+            const partyCombatPower = computePartyCombatPower(next);
             const zoneOrder = new Map(
               next.zones.map((z, index) => {
                 return [ z.id, index ];
@@ -1120,14 +1174,31 @@ export const GameProvider = ({
           next.autoAdventurer === true
           && next.prestige.purchasedUpgradeIds.includes("auto_adventurer")
         ) {
+          const maxAdventurerLevel = Math.max(
+            ...next.adventurers.
+              filter((a) => {
+                return a.unlocked;
+              }).
+              map((a) => {
+                return a.level;
+              }),
+          );
+          const autoBuyCap = 100;
           const [ bestAdventurer ] = next.adventurers.
             filter((adventurer) => {
               const cost
                 = adventurer.baseCost * Math.pow(1.15, adventurer.count);
-              return adventurer.unlocked && next.resources.gold >= cost;
+              const isMaxTier = adventurer.level === maxAdventurerLevel;
+              const withinCap
+                = isMaxTier || adventurer.count < autoBuyCap;
+              return (
+                adventurer.unlocked
+                && next.resources.gold >= cost
+                && withinCap
+              );
             }).
             sort((adventurerA, adventurerB) => {
-              return adventurerB.combatPower - adventurerA.combatPower;
+              return adventurerB.level - adventurerA.level;
             });
           if (bestAdventurer !== undefined) {
             const purchaseCost
@@ -1280,7 +1351,7 @@ export const GameProvider = ({
             if (enableNotificationsReference.current) {
               sendNotification("⭐ Prestige!", "You have ascended!");
             }
-            await reloadReference.current();
+            await reloadSilentReference.current();
           }).
           catch(() => {
 
@@ -1346,6 +1417,13 @@ export const GameProvider = ({
                 }
                 return afterBoss;
               });
+
+              /*
+               * Boss fight modifies server state; clear stale signature so
+               * the next pre-save or auto-save does not send a mismatched one.
+               */
+              signatureReference.current = null;
+              localStorage.removeItem("elysium_save_signature");
               setAutoBossLastResult({
                 at:       Date.now(),
                 bossName: bossName,
@@ -1789,7 +1867,18 @@ export const GameProvider = ({
 
   const collectExploration = useCallback(
     async(areaId: string): Promise<ExploreCollectResponse> => {
+      isSyncingReference.current = true;
       const result = await collectExplorationApi({ areaId });
+
+      /*
+       * Collect mutates server state outside the normal save flow — clear the
+       * stale HMAC signature and reset the timer so the next auto-save fires
+       * after React has re-rendered with the new materials in stateReference.
+       */
+      signatureReference.current = null;
+      localStorage.removeItem("elysium_save_signature");
+      lastSaveReference.current = Date.now();
+      isSyncingReference.current = false;
       setState((previous) => {
         if (previous?.exploration === undefined) {
           return previous;
@@ -2320,6 +2409,7 @@ export const GameProvider = ({
       offlineEssence,
       offlineGold,
       reload,
+      reloadSilent,
       resetProgress,
       saveSchemaVersion,
       schemaOutdated,