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/manaStore.ts

@@ -5,6 +5,9 @@ import { create } from 'zustand';
 import { persist } from 'zustand/middleware';
 import { ELEMENTS, MANA_PER_ELEMENT, BASE_UNLOCKED_ELEMENTS } from '../constants';
 import type { ElementState } from '../types';
+import { ok, okVoid, fail, ErrorCode } from '../utils/result';
+import { createSafeStorage } from '../utils/safe-persist';
+import type { Result } from '../utils/result';
 
 // ─── Mana State (data only) ─────────────────────────────────────────────────
 
@@ -29,12 +32,12 @@ export interface ManaActions {
   resetMeditateTicks: () => void;
 
   // Elements
-  convertMana: (element: string, amount: number) => boolean;
-  unlockElement: (element: string, cost: number) => boolean;
+  convertMana: (element: string, amount: number) => Result<{ converted: number }>;
+  unlockElement: (element: string, cost: number) => Result<void>;
   addElementMana: (element: string, amount: number, max: number) => void;
-  spendElementMana: (element: string, amount: number) => boolean;
+  spendElementMana: (element: string, amount: number) => Result<void>;
   setElementMax: (max: number) => void;
-  craftComposite: (target: string, recipe: string[]) => boolean;
+  craftComposite: (target: string, recipe: string[]) => Result<void>;
 
   // Helper for gameStore coordination
   processConvertAction: (rawMana: number) => { rawMana: number; elements: Record<string, ElementState> } | null;
@@ -110,11 +113,17 @@ export const useManaStore = create<ManaStore>()(
       convertMana: (element: string, amount: number) => {
         const state = get();
         const elem = state.elements[element];
-        if (!elem?.unlocked) return false;
+        if (!elem?.unlocked) {
+          return fail(ErrorCode.ELEMENT_NOT_UNLOCKED, `Element ${element} is not unlocked`);
+        }
 
         const cost = MANA_PER_ELEMENT * amount;
-        if (state.rawMana < cost) return false;
-        if (elem.current >= elem.max) return false;
+        if (state.rawMana < cost) {
+          return fail(ErrorCode.INSUFFICIENT_MANA, `Need ${cost} raw mana, have ${state.rawMana}`);
+        }
+        if (elem.current >= elem.max) {
+          return fail(ErrorCode.ELEMENT_MAX_CAPACITY, `Element ${element} is at max capacity`);
+        }
 
         const canConvert = Math.min(
           amount,
@@ -122,7 +131,9 @@ export const useManaStore = create<ManaStore>()(
           elem.max - elem.current
         );
 
-        if (canConvert <= 0) return false;
+        if (canConvert <= 0) {
+          return fail(ErrorCode.INVALID_INPUT, 'Cannot convert 0 or negative amount');
+        }
 
         set({
           rawMana: state.rawMana - canConvert * MANA_PER_ELEMENT,
@@ -132,13 +143,17 @@ export const useManaStore = create<ManaStore>()(
           },
         });
 
-        return true;
+        return ok({ converted: canConvert });
       },
 
       unlockElement: (element: string, cost: number) => {
         const state = get();
-        if (state.elements[element]?.unlocked) return false;
-        if (state.rawMana < cost) return false;
+        if (state.elements[element]?.unlocked) {
+          return fail(ErrorCode.INVALID_INPUT, `Element ${element} is already unlocked`);
+        }
+        if (state.rawMana < cost) {
+          return fail(ErrorCode.INSUFFICIENT_MANA, `Need ${cost} raw mana, have ${state.rawMana}`);
+        }
 
         set({
           rawMana: state.rawMana - cost,
@@ -148,7 +163,7 @@ export const useManaStore = create<ManaStore>()(
           },
         });
 
-        return true;
+        return okVoid();
       },
 
       addElementMana: (element: string, amount: number, max: number) => {
@@ -171,7 +186,12 @@ export const useManaStore = create<ManaStore>()(
       spendElementMana: (element: string, amount: number) => {
         const state = get();
         const elem = state.elements[element];
-        if (!elem || elem.current < amount) return false;
+        if (!elem) {
+          return fail(ErrorCode.INVALID_ELEMENT, `Element ${element} does not exist`);
+        }
+        if (elem.current < amount) {
+          return fail(ErrorCode.INSUFFICIENT_MANA, `Need ${amount} ${element} mana, have ${elem.current}`);
+        }
 
         set({
           elements: {
@@ -180,7 +200,7 @@ export const useManaStore = create<ManaStore>()(
           },
         });
 
-        return true;
+        return okVoid();
       },
 
       setElementMax: (max: number) => {
@@ -202,7 +222,9 @@ export const useManaStore = create<ManaStore>()(
 
         // Check if we have all ingredients
         for (const [r, amt] of Object.entries(costs)) {
-          if ((state.elements[r]?.current || 0) < amt) return false;
+          if ((state.elements[r]?.current || 0) < amt) {
+            return fail(ErrorCode.INSUFFICIENT_MANA, `Need ${amt} ${r} mana, have ${state.elements[r]?.current || 0}`);
+          }
         }
 
         // Deduct ingredients
@@ -223,7 +245,7 @@ export const useManaStore = create<ManaStore>()(
         };
 
         set({ elements: newElems });
-        return true;
+        return okVoid();
       },
 
       processConvertAction: (rawMana: number) => {
@@ -272,6 +294,7 @@ export const useManaStore = create<ManaStore>()(
       },
     }),
     {
+      storage: createSafeStorage(),
       name: 'mana-loop-mana',
       partialize: (state) => ({
         rawMana: state.rawMana,