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)

docs/circular-deps.txt

@@ -1,8 +1,8 @@
 # Circular Dependencies
-Generated: 2026-05-20T17:48:45.265Z
+Generated: 2026-05-20T19:05:27.642Z
 Found: 4 circular chain(s) — these MUST be fixed before modifying involved files.
 
-1. Processed 126 files (1.4s) (3 warnings)
+1. Processed 126 files (1.3s) (3 warnings)
 2. 1) stores/gameStore.ts > stores/gameActions.ts
 3. 2) stores/gameStore.ts > stores/gameLoopActions.ts
 4. 3) stores/gameStore.ts > stores/tick-pipeline.ts