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/crafting-equipment.ts

@@ -5,6 +5,8 @@ import type { EquipmentInstance, EquipmentCraftingProgress } from './types';
 import { CRAFTING_RECIPES, canCraftRecipe, type CraftingRecipe } from './data/crafting-recipes';
 import { EQUIPMENT_TYPES } from './data/equipment';
 import { generateInstanceId } from './crafting-utils';
+import { ok, fail, ErrorCode } from './utils/result';
+import type { Result } from './utils/result';
 
 // ─── Equipment Crafting Validation ──────────────────────────────────────────
 
@@ -110,14 +112,14 @@ export function calculateCraftingTick(currentProgress: number, required: number)
 export function completeEquipmentCrafting(
   blueprintId: string,
   recipe: CraftingRecipe
-): {
+): Result<{
   instanceId: string;
   instance: EquipmentInstance;
   logMessage: string;
-} {
+}> {
   const equipType = EQUIPMENT_TYPES[recipe.equipmentTypeId];
   if (!equipType) {
-    throw new Error(`Invalid equipment type: ${recipe.equipmentTypeId}`);
+    return fail(ErrorCode.INVALID_EQUIPMENT_TYPE, `Invalid equipment type: ${recipe.equipmentTypeId}`);
   }
 
   const instanceId = `equip_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
@@ -133,11 +135,11 @@ export function completeEquipmentCrafting(
     tags: [],
   };
 
-  return {
+  return ok({
     instanceId,
     instance: newInstance,
     logMessage: `🔨 Crafted ${recipe.name}!`,
-  };
+  });
 }
 
 // ─── Crafting Cancellation ──────────────────────────────────────────────────