test: migrate to MSW testing architecture for App integration test

Major testing infrastructure upgrade from manual mocks to Mock Service Worker (MSW):

New MSW infrastructure (tests/msw/):
- Add state.ts: In-memory state manager with full CRUD operations
  - Manage providers and current selections per app type (Claude/Codex)
  - Auto-switch current provider when deleted
  - Deep clone to prevent reference pollution
- Add handlers.ts: HTTP request handlers for 10 Tauri API endpoints
  - Mock get_providers, switch_provider, add/update/delete_provider
  - Mock update_sort_order, update_tray_menu, import_default_config
  - Support error scenarios (404 for non-existent providers)
- Add tauriMocks.ts: Tauri API mock layer
  - Transparently convert invoke() calls to HTTP requests
  - Mock event listener system with emitTauriEvent helper
  - Use cross-fetch for Node.js environment
- Add server.ts: MSW server setup for Node.js test environment

Refactor App.test.tsx (-170 lines, -43%):
- Remove 23 manual mocks (useProvidersQuery, useProviderActions, etc.)
- Run real hooks with MSW-backed API calls instead of mock implementations
- Test real state changes instead of mock call counts
- Add comprehensive flow: duplicate → create → edit → delete → event listening
- Verify actual provider list changes and current selection updates

Setup integration:
- Add MSW server lifecycle to tests/setupTests.ts
  - Start server before all tests
  - Reset handlers and state after each test
  - Close server after all tests complete
- Clear all mocks in afterEach for test isolation

Dependencies:
- Add msw@^2.11.6 for API mocking
- Add cross-fetch@^4.1.0 for fetch polyfill in Node.js

Type fixes:
- Add missing imports (AppType, Provider) in handlers.ts
- Fix HttpResponse.json generic constraint with as any (MSW best practice)
- Change invalid category "default" to "official" in state.ts

Test results: All 50 tests passing across 8 files, 0 TypeScript errors

tests/msw/state.ts

@@ -0,0 +1,116 @@
+import type { AppType } from "@/lib/api/types";
+import type { Provider } from "@/types";
+
+type ProvidersByApp = Record<AppType, Record<string, Provider>>;
+type CurrentProviderState = Record<AppType, string>;
+
+const createDefaultProviders = (): ProvidersByApp => ({
+  claude: {
+    "claude-1": {
+      id: "claude-1",
+      name: "Claude Default",
+      settingsConfig: {},
+      category: "official",
+      sortIndex: 0,
+      createdAt: Date.now(),
+    },
+    "claude-2": {
+      id: "claude-2",
+      name: "Claude Custom",
+      settingsConfig: {},
+      category: "custom",
+      sortIndex: 1,
+      createdAt: Date.now() + 1,
+    },
+  },
+  codex: {
+    "codex-1": {
+      id: "codex-1",
+      name: "Codex Default",
+      settingsConfig: {},
+      category: "official",
+      sortIndex: 0,
+      createdAt: Date.now(),
+    },
+    "codex-2": {
+      id: "codex-2",
+      name: "Codex Secondary",
+      settingsConfig: {},
+      category: "custom",
+      sortIndex: 1,
+      createdAt: Date.now() + 1,
+    },
+  },
+});
+
+const createDefaultCurrent = (): CurrentProviderState => ({
+  claude: "claude-1",
+  codex: "codex-1",
+});
+
+let providers = createDefaultProviders();
+let current = createDefaultCurrent();
+
+const cloneProviders = (value: ProvidersByApp) =>
+  JSON.parse(JSON.stringify(value)) as ProvidersByApp;
+
+export const resetProviderState = () => {
+  providers = createDefaultProviders();
+  current = createDefaultCurrent();
+};
+
+export const getProviders = (appType: AppType) =>
+  cloneProviders(providers)[appType] ?? {};
+
+export const getCurrentProviderId = (appType: AppType) => current[appType] ?? "";
+
+export const setCurrentProviderId = (appType: AppType, providerId: string) => {
+  current[appType] = providerId;
+};
+
+export const updateProviders = (appType: AppType, data: Record<string, Provider>) => {
+  providers[appType] = cloneProviders({ [appType]: data } as ProvidersByApp)[appType];
+};
+
+export const setProviders = (appType: AppType, data: Record<string, Provider>) => {
+  providers[appType] = JSON.parse(JSON.stringify(data)) as Record<string, Provider>;
+};
+
+export const addProvider = (appType: AppType, provider: Provider) => {
+  providers[appType] = providers[appType] ?? {};
+  providers[appType][provider.id] = provider;
+};
+
+export const updateProvider = (appType: AppType, provider: Provider) => {
+  if (!providers[appType]) return;
+  providers[appType][provider.id] = {
+    ...providers[appType][provider.id],
+    ...provider,
+  };
+};
+
+export const deleteProvider = (appType: AppType, providerId: string) => {
+  if (!providers[appType]) return;
+  delete providers[appType][providerId];
+  if (current[appType] === providerId) {
+    const fallback = Object.keys(providers[appType])[0] ?? "";
+    current[appType] = fallback;
+  }
+};
+
+export const updateSortOrder = (
+  appType: AppType,
+  updates: { id: string; sortIndex: number }[],
+) => {
+  if (!providers[appType]) return;
+  updates.forEach(({ id, sortIndex }) => {
+    const provider = providers[appType][id];
+    if (provider) {
+      providers[appType][id] = { ...provider, sortIndex };
+    }
+  });
+};
+
+export const listProviders = (appType: AppType) =>
+  JSON.parse(JSON.stringify(providers[appType] ?? {})) as Record<string, Provider>;
+