feat: 支持 AI 设计项目多会话交互

需求：用户可在同一设计项目中新建和切换会话，任务列表保持项目级共享。

实现：
- 增加会话选择、新建入口及本地数据迁移
- Conversation 独立消息、Brief、Quote 与流式状态
- 保留项目任务并修复 Task revision 与 ABA 异步竞态
- 保持 Enter 发送、Shift+Enter 换行及 IME 保护

tests/unit/image-workspace-route.test.ts

@@ -130,6 +130,8 @@ describe('AI design Main route boundary', () => {
     const workspace = {
       bootstrap: vi.fn().mockResolvedValue(bootstrap),
       createWorkspace: vi.fn().mockResolvedValue({ workspaceId: 'workspace-one' }),
+      createConversation: vi.fn(),
+      getConversation: vi.fn(),
       renameWorkspace: vi.fn(),
       getWorkspace: vi.fn(),
       submitMessage: vi.fn().mockResolvedValue({ workspaceId: 'workspace/one' }),
@@ -177,12 +179,13 @@ describe('AI design Main route boundary', () => {
       }),
       messageResponse.res,
       new URL(
-        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/messages',
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/conversations/conversation%2Fone/messages',
       ),
       ctx,
     );
     expect(workspace.submitMessage).toHaveBeenCalledWith({
       workspaceId: 'workspace/one',
+      conversationId: 'conversation/one',
       clientTurnId: 'turn-one',
       expectedTurnRevision: 3,
       message: '继续编辑',
@@ -221,12 +224,13 @@ describe('AI design Main route boundary', () => {
       }),
       confirmResponse.res,
       new URL(
-        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/quotes/quote%2Fone/confirm',
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/conversations/conversation%2Fone/quotes/quote%2Fone/confirm',
       ),
       ctx,
     );
     expect(workspace.confirmGeneration).toHaveBeenCalledWith({
       workspaceId: 'workspace/one',
+      conversationId: 'conversation/one',
       quoteId: 'quote/one',
       clientTurnId: 'turn-two',
       expectedTurnRevision: 4,
@@ -391,6 +395,7 @@ describe('AI design Main route boundary', () => {
           generationTask: {
             taskId: 'task-live',
             workspaceId: 'workspace/one',
+            conversationId: 'conversation/one',
             medium: 'image' as const,
             status: 'succeeded' as const,
             briefVersion: 1,
@@ -414,7 +419,7 @@ describe('AI design Main route boundary', () => {
       request,
       response as unknown as ServerResponse,
       new URL(
-        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/events',
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace%2Fone/conversations/conversation%2Fone/events',
       ),
       { imageWorkspace: { openWorkspaceEvents } } as unknown as HostApiContext,
     );
@@ -422,6 +427,7 @@ describe('AI design Main route boundary', () => {
     expect(handled).toBe(true);
     expect(openWorkspaceEvents).toHaveBeenCalledWith({
       workspaceId: 'workspace/one',
+      conversationId: 'conversation/one',
       afterEventId: 'session-one:6',
     });
     expect(response.statusCode).toBe(200);