feat: add zone-scaled quest failure chance

Quests now have a random chance of failing when their timer expires.
On failure the quest resets to available (no rewards lost, just time).
Failure chance scales by zone: 10% in Verdant Vale up to 40% in the
end-game zones. The Quest type gains lastFailedAt so the UI can show
a warning on subsequent attempts.

apps/web/src/components/game/QuestPanel.tsx

@@ -60,6 +60,9 @@ const QuestCard = ({ quest, partyCombatPower, unlockHint, zoneHint }: QuestCardP
             {!zoneHint && unlockHint && <p className="unlock-hint">📜 Complete: {unlockHint}</p>}
           </>
         )}
+        {quest.status === "available" && quest.lastFailedAt != null && (
+          <p className="quest-failed-hint">⚠️ Last attempt failed</p>
+        )}
         {quest.status === "available" && (
           <button
             className="start-quest-button"

apps/web/src/engine/tick.ts

@@ -46,6 +46,32 @@ const checkAchievements = (state: GameState): Achievement[] => {
 /** Maximum value any resource can accumulate to. Beyond this JS floats lose all useful precision. */
 export const RESOURCE_CAP = 1e300;
 
+/**
+ * Probability of quest failure per zone — scales from 10% (early game) to 40% (end game).
+ * On failure the quest resets to "available" with no rewards; the player must wait the
+ * full duration again on their next attempt.
+ */
+const ZONE_FAILURE_CHANCE: Record<string, number> = {
+  verdant_vale: 0.10,
+  shattered_ruins: 0.12,
+  frozen_peaks: 0.14,
+  shadow_marshes: 0.16,
+  volcanic_depths: 0.18,
+  astral_void: 0.20,
+  celestial_reaches: 0.22,
+  abyssal_trench: 0.24,
+  infernal_court: 0.26,
+  crystalline_spire: 0.28,
+  void_sanctum: 0.30,
+  eternal_throne: 0.32,
+  primordial_chaos: 0.34,
+  infinite_expanse: 0.36,
+  reality_forge: 0.38,
+  cosmic_maelstrom: 0.40,
+  primeval_sanctum: 0.40,
+  the_absolute: 0.40,
+};
+
 const capResource = (value: number): number => Math.min(value, RESOURCE_CAP);
 
 /**
@@ -128,6 +154,11 @@ export const applyTick = (state: GameState, deltaSeconds: number): GameState =>
       return quest;
     }
 
+    const failureChance = ZONE_FAILURE_CHANCE[quest.zoneId] ?? 0.20;
+    if (Math.random() < failureChance) {
+      return { ...quest, status: "available" as const, startedAt: undefined, lastFailedAt: now };
+    }
+
     for (const reward of quest.rewards) {
       if (reward.type === "gold" && reward.amount != null) {
         questGold += reward.amount;

apps/web/src/styles.css

@@ -1156,6 +1156,14 @@ body {
   margin-top: 0.2rem;
 }
 
+.quest-failed-hint {
+  color: #e6a817;
+  font-size: 0.75rem;
+  font-style: italic;
+  margin-bottom: 0.25rem;
+  margin-top: 0;
+}
+
 .unlock-hint {
   color: var(--colour-text-muted);
   font-size: 0.75rem;

packages/types/src/interfaces/Quest.ts

@@ -25,4 +25,6 @@ export interface Quest {
   zoneId: string;
   /** Minimum party combat power required to start this quest */
   combatPowerRequired?: number;
+  /** Unix timestamp of the most recent failed attempt (if any) */
+  lastFailedAt?: number;
 }