feat: support runestone rewards in achievement system (#190)

- Add runestones field to AchievementReward type
- Update tick engine to accumulate and apply runestone rewards
  when achievements unlock, alongside the existing crystal rewards

apps/web/src/engine/tick.ts

@@ -11,7 +11,6 @@
 /* eslint-disable max-lines -- Engine file necessarily exceeds line limit */
 /* eslint-disable import/group-exports -- Exports appear alongside their definitions for readability */
 /* eslint-disable import/exports-last -- Exports appear alongside their definitions for readability */
-/* eslint-disable unicorn/no-array-reduce -- reduce is the most readable approach for multiplier chains */
 /* eslint-disable max-nested-callbacks -- Tick engine requires nested array operations for game logic */
 import {
   type Achievement,
@@ -818,23 +817,29 @@ export const applyTick = (
     zones:    updatedZones,
   };
 
-  // Check achievements and apply crystal rewards for newly unlocked ones
+  // Check achievements and apply crystal and runestone rewards for newly unlocked ones
   const updatedAchievements = checkAchievements(partialState);
-  const crystalsFromAchievements = updatedAchievements.reduce(
+  let crystalsFromAchievements = 0;
-    (sum, achievement, index) => {
+  let runestonesFromAchievements = 0;
+  for (const [ index, achievement ] of updatedAchievements.entries()) {
     const wasLocked = state.achievements[index]?.unlockedAt === null;
     const isNowUnlocked = achievement.unlockedAt !== null;
     if (wasLocked && isNowUnlocked) {
-        return sum + (achievement.reward?.crystals ?? 0);
+      crystalsFromAchievements
+        = crystalsFromAchievements + (achievement.reward?.crystals ?? 0);
+      runestonesFromAchievements
+        = runestonesFromAchievements + (achievement.reward?.runestones ?? 0);
+    }
   }
-      return sum;
-    },
-    0,
-  );
 
   return {
     ...partialState,
     achievements: updatedAchievements,
+    prestige:     {
+      ...partialState.prestige,
+      runestones:
+        partialState.prestige.runestones + runestonesFromAchievements,
+    },
     resources: {
       ...partialState.resources,
       crystals: capResource(

packages/types/src/interfaces/achievement.ts

@@ -21,6 +21,7 @@ interface AchievementCondition {
 
 interface AchievementReward {
   crystals?:   number;
+  runestones?: number;
 }
 
 interface Achievement {