refactor(server): 消除与 Core 的重复类型定义

- 删除 Server 中 60+ 个与 Core 重复的类型定义
- 将动态导入 (await import) 改为静态类型导入 (import type)
- 保留必要的运行时静态导入
- 修复测试文件中的 mock 初始化问题
- 净删除约 960 行重复代码

重构文件:
- routes/checkpoints.ts: 删除 155 行重复类型
- routes/agents.ts: 删除 93 行重复类型
- routes/commands.ts: 删除 83 行重复类型
- routes/mcp.ts: 修复类型窄化
- routes/hooks.ts: 已使用静态导入
- routes/providers.ts: 删除 63 行重复类型
- session/manager.ts: 删除 41 行重复类型
- routes/sessions.ts: 添加类型导入
- permission/handler.ts: 添加类型导入

packages/server/tests/unit/routes/agents.test.ts

@@ -34,15 +34,7 @@ const mockAgentModule = vi.hoisted(() => ({
   isPresetAgent: vi.fn((name: string) => name in mockPresetAgents),
 }));
 
-// Track if module should be available
-let moduleAvailable = true;
-
-vi.mock('@ai-assistant/core', () => {
-  if (!moduleAvailable) {
-    throw new Error('Module not found');
-  }
-  return mockAgentModule;
-});
+vi.mock('@ai-assistant/core', () => mockAgentModule);
 
 vi.mock('../../../src/routes/config.js', () => ({
   getConfig: vi.fn(() => ({ workdir: '/test/workdir' })),
@@ -57,7 +49,6 @@ app.route('/agents', agentsRouter);
 describe('Agents Route', () => {
   beforeEach(() => {
     vi.clearAllMocks();
-    moduleAvailable = true;
     mockAgentModule.loadAgentConfig.mockResolvedValue(null);
     mockAgentModule.saveAgentConfig.mockResolvedValue(undefined);
   });

packages/server/tests/unit/routes/commands.test.ts

@@ -35,15 +35,7 @@ const mockCommandModule = vi.hoisted(() => ({
   createCommandManager: vi.fn(() => mockCommandManager),
 }));
 
-// Track if module should be available
-let moduleAvailable = true;
-
-vi.mock('@ai-assistant/core', () => {
-  if (!moduleAvailable) {
-    throw new Error('Module not found');
-  }
-  return mockCommandModule;
-});
+vi.mock('@ai-assistant/core', () => mockCommandModule);
 
 vi.mock('../../../src/routes/config.js', () => ({
   getConfig: vi.fn(() => ({ workdir: '/test/workdir' })),
@@ -58,7 +50,6 @@ app.route('/commands', commandsRouter);
 describe('Commands Route', () => {
   beforeEach(() => {
     vi.clearAllMocks();
-    moduleAvailable = true;
     mockCommandRegistry.list.mockReturnValue([]);
     mockCommandRegistry.getStats.mockReturnValue({ total: 0, bySource: {} });
   });

packages/server/tests/unit/routes/hooks.test.ts

@@ -15,15 +15,7 @@ const mockHooksModule = vi.hoisted(() => ({
   createDefaultConfig: vi.fn(),
 }));
 
-// Track if module should be available
-let moduleAvailable = true;
-
-vi.mock('@ai-assistant/core', () => {
-  if (!moduleAvailable) {
-    throw new Error('Module not found');
-  }
-  return mockHooksModule;
-});
+vi.mock('@ai-assistant/core', () => mockHooksModule);
 
 vi.mock('../../../src/routes/config.js', () => ({
   getConfig: vi.fn(() => ({ workdir: '/test/workdir' })),
@@ -44,7 +36,6 @@ app.route('/hooks', hooksRouter);
 describe('Hooks Route', () => {
   beforeEach(() => {
     vi.clearAllMocks();
-    moduleAvailable = true;
     mockHooksModule.loadHookConfig.mockResolvedValue(null);
     mockHooksModule.getConfigFilePath.mockResolvedValue('/test/workdir/.ai-assistant.json');
   });

packages/server/tests/unit/routes/providers.test.ts

@@ -26,15 +26,7 @@ const mockCoreModule = vi.hoisted(() => ({
   getProviderRegistry: vi.fn(() => mockRegistry),
 }));
 
-// Track if core module should be available
-let coreModuleAvailable = true;
-
-vi.mock('@ai-assistant/core', () => {
-  if (!coreModuleAvailable) {
-    throw new Error('Module not found');
-  }
-  return mockCoreModule;
-});
+vi.mock('@ai-assistant/core', () => mockCoreModule);
 
 import { providersRouter } from '../../../src/routes/providers.js';
 
@@ -45,7 +37,6 @@ app.route('/providers', providersRouter);
 describe('Providers Route', () => {
   beforeEach(() => {
     vi.clearAllMocks();
-    coreModuleAvailable = true;
   });
 
   describe('GET /providers - 列出所有提供商', () => {