refactor: complete error handling standardization (issue #101)

Prestige Store:
- Convert doPrestige() to return Result<void> with specific error codes
  (INVALID_PRESTIGE_ID, PRESTIGE_MAX_LEVEL, INSUFFICIENT_INSIGHT)
- Convert startPactRitual() to return Result<void> with specific error codes
  (GUARDIAN_NOT_DEFEATED, PACT_ALREADY_SIGNED, PACT_SLOTS_FULL,
   INSUFFICIENT_MANA, RITUAL_IN_PROGRESS)

Combat Actions:
- Add try/catch wrapper inside processCombatTick with safe fallback defaults
- Add makeDefaultCombatTickResult helper for error recovery

LocalStorage Error Handling:
- Create safe-persist.ts utility wrapping localStorage with error handling
  (corrupted JSON, quota exceeded, unexpected failures)
- Update all 8 Zustand stores to use createSafeStorage() in persist middleware

UI Updates:
- Update GuardianPactsTab to use Result pattern for ritual error messages

Tests:
- Update store-actions-combat-prestige.test.ts for Result return types
- Update store-actions.test.ts ManaStore tests for Result pattern
- Remove duplicate Prestige/Discipline sections from store-actions.test.ts
- All files under 400 line limit

601 tests pass (3 pre-existing failures in spire-utils.test.ts)

src/lib/game/stores/gameStore.ts

@@ -31,6 +31,7 @@ import { useCraftingStore } from './craftingStore';
 import { useDisciplineStore } from './discipline-slice';
 import { ATTUNEMENTS_DEF, getAttunementConversionRate } from '../data/attunements';
 import { createResetGame, createGatherMana } from './gameActions';
+import { createSafeStorage } from '../utils/safe-persist';
 import { createStartNewLoop } from './gameLoopActions';
 import { buildTickContext, applyTickWrites } from './tick-pipeline';
 import type { TickContext, TickWrites } from './tick-pipeline';
@@ -70,19 +71,20 @@ export const useGameStore = create<GameCoordinatorStore>()(
       },
 
       tick: () => {
-        // ── Phase 1: Read — snapshot all store states once ──────────────────
-        const ctx = buildTickContext({
-          game: get(),
-          ui: useUIStore.getState(),
-          prestige: usePrestigeStore.getState(),
-          mana: useManaStore.getState(),
-          combat: useCombatStore.getState(),
-          crafting: useCraftingStore.getState(),
-          attunement: useAttunementStore.getState(),
-          discipline: useDisciplineStore.getState(),
-        });
+        try {
+          // ── Phase 1: Read — snapshot all store states once ──────────────────
+          const ctx = buildTickContext({
+            game: get(),
+            ui: useUIStore.getState(),
+            prestige: usePrestigeStore.getState(),
+            mana: useManaStore.getState(),
+            combat: useCombatStore.getState(),
+            crafting: useCraftingStore.getState(),
+            attunement: useAttunementStore.getState(),
+            discipline: useDisciplineStore.getState(),
+          });
 
-        if (ctx.ui.gameOver || ctx.ui.paused) return;
+          if (ctx.ui.gameOver || ctx.ui.paused) return;
 
         // ── Phase 2: Compute — derive all updates ───────────────────────────
         const writes: TickWrites = { logs: [] };
@@ -322,6 +324,14 @@ export const useGameStore = create<GameCoordinatorStore>()(
           setDiscipline: (w) => useDisciplineStore.setState(w),
           addLogs: (msgs) => msgs.forEach((m) => useUIStore.getState().addLog(m)),
         });
+        } catch (error) {
+          // Log error to UI store if available, otherwise console error
+          try {
+            useUIStore.getState().addLog(`⚠️ Tick error: ${error.message}`);
+          } catch {
+            console.error('Tick error:', error);
+          }
+        }
       },
 
       resetGame: createResetGame(set, initialState),
@@ -332,6 +342,7 @@ export const useGameStore = create<GameCoordinatorStore>()(
       gatherMana: createGatherMana(),
     }),
     {
+      storage: createSafeStorage(),
       name: 'mana-loop-game-storage',
       partialize: (state) => ({
         day: state.day,