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

.project-docs/30-worklog/tasks/20260806-design-multisession-ui-4e7d.md

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+# Task: AI 设计项目多会话客户端
+
+## Identity
+
+- Task ID: 20260806-design-multisession-ui-4e7d
+- Mode: Feature
+- Branch: codex/20260806-design-multisession-ui-4e7d-design-multisession-ui
+- Worktree: D:\Datas\OthersProjects\makelore-design-multisession-4e7d
+- Base commit: 498089401708dc08123141891dba9b54e47cefea
+- Owner: codex
+- Status: Completed
+
+## Scope
+
+- Extend the shared AI Design contract with project Conversations and Conversation-tagged events/tasks.
+- Add Electron adapter and host API support for listing, creating, reading and submitting to a Conversation.
+- Add renderer store state/actions for the active Conversation and protect asynchronous/streaming updates with Workspace + Conversation identity.
+- Add a compact Conversation selector and “new conversation” action to AI Design while leaving the generation-task panel project-scoped.
+- Migrate the local fallback Workspace data model to create a default Conversation.
+- Cover adapter, route, store and page behavior, including Conversation switching and project-level task persistence.
+
+## Intent And Constraints
+
+- Product model: one design project contains multiple independent conversations; starting a new conversation must not create a new project.
+- The selected Conversation owns messages, Brief, Quote and `turnRevision`; changing Conversations must not leak pending or streaming text.
+- Generation tasks and assets belong to the project and remain visible when the selected Conversation changes.
+- Each Conversation uses its stable Gateway Session/stream. Switching Conversation reconnects to that Session without changing projects; task events delivered on any Conversation stream are still reduced by `workspaceId` only.
+- Preserve compatibility with the deployed single-conversation server during rollout where practical, without retaining two sources of client state.
+- Keep the existing visual language and input behavior, including Enter to send, Shift+Enter for newline and IME composition protection.
+
+## Outcome
+
+- Split the client model into Workspace, Conversation and Workspace-owned generation tasks, including local v2-to-v3 migration of the previous single chat into a default historical Conversation.
+- Added Electron/host APIs for Conversation list/create/read/turn/confirm/event flows and reused the server-owned persistent Gateway Session for each Conversation.
+- Added active Conversation state, guarded async/stream updates by Workspace + Conversation identity, and preserved the Workspace task list while switching chats.
+- Added generation-token and monotonic-revision guards for Conversation/Workspace ABA races, including late failures.
+- Task event watermarks now advance only from real stream events; REST freshness continues to use per-task `updatedAt`.
+- Added Conversation switching and new-Conversation actions to both the AI Design header and expanded project sidebar, with a global in-flight guard against duplicate creation.
+- Preserved composer keyboard behavior: Enter sends, Shift+Enter inserts a newline, and IME composition Enter is ignored.
+
+## Verification
+
+- TypeScript `tsc --noEmit`: passed.
+- Focused AI Design suites: `7 files / 93 tests passed`, including all 19 migrated adapter behavior tests.
+- ESLint for all changed TypeScript/TSX files: passed.
+- Production Vite + Electron build: passed; only existing chunk-size/dynamic-import warnings remain.
+- Full Vitest run is not green on the base environment: 19 failures reproduce in the original client tree (missing `zip`/`.opencode` resources and existing timing checks); one additional speech-transcription test is outside this task's diff and passes only with the user's uncommitted original-tree changes.
+
+## Follow-ups
+
+- Publish only after server migration `0033` and the multi-conversation API are live.
+- Consider pagination/search when a project grows beyond the six recent Conversations shown inline in the sidebar.
+
+## Promotion Candidates
+
+- Promote Workspace/Conversation/Task client-state ownership and stream routing into the canonical client architecture/current-state documents during integration.