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/prestigeStore.ts

@@ -3,8 +3,11 @@
 
 import { create } from 'zustand';
 import { persist } from 'zustand/middleware';
+import { createSafeStorage } from '../utils/safe-persist';
 import type { Memory } from '../types';
 import { GUARDIANS, PRESTIGE_DEF } from '../constants';
+import { ok, okVoid, fail, ErrorCode } from '../utils/result';
+import type { Result } from '../utils/result';
 
 // ─── Prestige State (data only) ──────────────────────────────────────────────
 
@@ -41,11 +44,11 @@ export interface PrestigeState {
 // ─── Prestige Actions ────────────────────────────────────────────────────────
 
 export interface PrestigeActions {
-  doPrestige: (id: string) => boolean;
+  doPrestige: (id: string) => Result<void>;
   addMemory: (memory: Memory) => void;
   removeMemory: (skillId: string) => void;
   clearMemories: () => void;
-  startPactRitual: (floor: number, rawMana: number) => boolean;
+  startPactRitual: (floor: number, rawMana: number) => Result<void>;
   cancelPactRitual: () => void;
   completePactRitual: (addLog: (msg: string) => void) => void;
   updatePactRitualProgress: (hours: number) => void;
@@ -112,10 +115,11 @@ export const usePrestigeStore = create<PrestigeStore>()(
       doPrestige: (id: string) => {
         const state = get();
         const pd = PRESTIGE_DEF[id];
-        if (!pd) return false;
+        if (!pd) return fail(ErrorCode.INVALID_PRESTIGE_ID, `Unknown prestige upgrade: ${id}`);
 
         const lvl = state.prestigeUpgrades[id] || 0;
-        if (lvl >= pd.max || state.insight < pd.cost) return false;
+        if (lvl >= pd.max) return fail(ErrorCode.PRESTIGE_MAX_LEVEL, `Upgrade ${id} is already at max level (${pd.max})`);
+        if (state.insight < pd.cost) return fail(ErrorCode.INSUFFICIENT_INSIGHT, `Need ${pd.cost} insight, have ${state.insight}`);
 
         const newPU = { ...state.prestigeUpgrades, [id]: lvl + 1 };
         set({
@@ -124,7 +128,7 @@ export const usePrestigeStore = create<PrestigeStore>()(
           memorySlots: id === 'deepMemory' ? state.memorySlots + 1 : state.memorySlots,
           pactSlots: id === 'pactBinding' ? state.pactSlots + 1 : state.pactSlots,
         });
-        return true;
+        return okVoid();
       },
 
       addMemory: (memory: Memory) => {
@@ -148,19 +152,19 @@ export const usePrestigeStore = create<PrestigeStore>()(
       startPactRitual: (floor: number, rawMana: number) => {
         const state = get();
         const guardian = GUARDIANS[floor];
-        if (!guardian) return false;
+        if (!guardian) return fail(ErrorCode.INVALID_INPUT, `No guardian at floor ${floor}`);
 
-        if (!state.defeatedGuardians.includes(floor)) return false;
-        if (state.signedPacts.includes(floor)) return false;
-        if (state.signedPacts.length >= state.pactSlots) return false;
-        if (rawMana < guardian.pactCost) return false;
-        if (state.pactRitualFloor !== null) return false;
+        if (!state.defeatedGuardians.includes(floor)) return fail(ErrorCode.GUARDIAN_NOT_DEFEATED, `Guardian at floor ${floor} has not been defeated`);
+        if (state.signedPacts.includes(floor)) return fail(ErrorCode.PACT_ALREADY_SIGNED, `Pact with ${guardian.name} is already signed`);
+        if (state.signedPacts.length >= state.pactSlots) return fail(ErrorCode.PACT_SLOTS_FULL, `All pact slots are full (${state.pactSlots})`);
+        if (rawMana < guardian.pactCost) return fail(ErrorCode.INSUFFICIENT_MANA, `Need ${guardian.pactCost} raw mana, have ${rawMana}`);
+        if (state.pactRitualFloor !== null) return fail(ErrorCode.RITUAL_IN_PROGRESS, `A pact ritual is already in progress for floor ${state.pactRitualFloor}`);
 
         set({
           pactRitualFloor: floor,
           pactRitualProgress: 0,
         });
-        return true;
+        return okVoid();
       },
 
       cancelPactRitual: () => {
@@ -291,6 +295,7 @@ export const usePrestigeStore = create<PrestigeStore>()(
       },
     }),
     {
+      storage: createSafeStorage(),
       name: 'mana-loop-prestige',
       partialize: (state) => ({
         loopCount: state.loopCount,