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

electron/api/routes/image-workspace.ts

@@ -11,6 +11,7 @@ import {
   IMAGE_WORKSPACE_UNAVAILABLE_CODE,
   IMAGE_WORKSPACE_UNAVAILABLE_MESSAGE,
   type DesignAssetUploadInput,
+  type DesignCreateConversationInput,
   type DesignConfirmGenerationInput,
   type DesignCreateWorkspaceInput,
   type DesignRenameWorkspaceInput,
@@ -283,6 +284,7 @@ async function relayWorkspaceEvents(
   res: ServerResponse,
   ctx: HostApiContext,
   workspaceId: string,
+  conversationId: string,
 ): Promise<void> {
   if (!ctx.imageWorkspace?.openWorkspaceEvents) {
     throw new DesignWorkspaceModuleError(
@@ -295,6 +297,7 @@ async function relayWorkspaceEvents(
   const afterEventId = Array.isArray(header) ? header[0] : header;
   const subscription = await ctx.imageWorkspace.openWorkspaceEvents({
     workspaceId,
+    conversationId,
     ...(afterEventId ? { afterEventId } : {}),
   });
   let closed = false;
@@ -399,11 +402,35 @@ export async function handleImageWorkspaceRoutes(
 
     if (segments.length === 3
       && segments[0] === 'workspaces'
-      && segments[2] === 'messages'
+      && segments[2] === 'conversations'
+      && req.method === 'POST') {
+      const body = await parseJsonBody<Record<string, unknown>>(req);
+      const input: DesignCreateConversationInput = {
+        workspaceId: segments[1],
+        clientConversationId: asString(body.clientConversationId),
+        title: asString(body.title),
+      };
+      sendData(res, await ctx.imageWorkspace.createConversation(input));
+      return true;
+    }
+
+    if (segments.length === 4
+      && segments[0] === 'workspaces'
+      && segments[2] === 'conversations'
+      && req.method === 'GET') {
+      sendData(res, await ctx.imageWorkspace.getConversation(segments[1], segments[3]));
+      return true;
+    }
+
+    if (segments.length === 5
+      && segments[0] === 'workspaces'
+      && segments[2] === 'conversations'
+      && segments[4] === 'messages'
       && req.method === 'POST') {
       const body = await parseJsonBody<Record<string, unknown>>(req);
       const input: DesignSubmitMessageInput = {
         workspaceId: segments[1],
+        conversationId: segments[3],
         clientTurnId: asString(body.clientTurnId),
         expectedTurnRevision: asInteger(body.expectedTurnRevision),
         message: asString(body.message),
@@ -440,23 +467,26 @@ export async function handleImageWorkspaceRoutes(
       return true;
     }
 
-    if (segments.length === 3
+    if (segments.length === 5
       && segments[0] === 'workspaces'
-      && segments[2] === 'events'
+      && segments[2] === 'conversations'
+      && segments[4] === 'events'
       && req.method === 'GET') {
-      await relayWorkspaceEvents(req, res, ctx, segments[1]);
+      await relayWorkspaceEvents(req, res, ctx, segments[1], segments[3]);
       return true;
     }
 
-    if (segments.length === 5
+    if (segments.length === 7
       && segments[0] === 'workspaces'
-      && segments[2] === 'quotes'
-      && segments[4] === 'confirm'
+      && segments[2] === 'conversations'
+      && segments[4] === 'quotes'
+      && segments[6] === 'confirm'
       && req.method === 'POST') {
       const body = await parseJsonBody<Record<string, unknown>>(req);
       const input: DesignConfirmGenerationInput = {
         workspaceId: segments[1],
-        quoteId: segments[3],
+        conversationId: segments[3],
+        quoteId: segments[5],
         clientTurnId: asString(body.clientTurnId),
         expectedTurnRevision: asInteger(body.expectedTurnRevision),
       };