feat: align local-first workspace direction

Document the VSCode-like local-first product shape, demote Convex to a control-plane role, and retire stale architecture drafts.

Add local workspace migration/export references plus smoke coverage for no-Convex managed workspace startup, local markdown title/body/options persistence, asset upload behavior, and Convex fixture export.

Verification: git diff --cached --check; node scripts/check-local-first-convex-guard.js --staged; node scripts/task444-convex-workspace-export-local-fixture-smoke.js; node scripts/task166-local-first-managed-workspace-no-convex-smoke.js; node scripts/task167-local-markdown-title-body-options-no-convex-smoke.js

design/README.md

@@ -1,6 +1,11 @@
 # design 设计稿索引
 
-> 更新时间：2026-05-14
+> 更新时间：2026-05-19
+>
+> 当前产品口径：`VSCode 简化版工作区 + tiptap 的 Markdown 前端编辑器 + Hermes/Reasonix agent + simplemindmap/office 插件 + Wolai 主题 Web 壳 + 鉴权控制面`。
+>
+> 当前上位主线：local-first workspace 是默认数据形态，本地 `.md` 是页面正文真相，Convex / 服务端只作为控制面、cloud source、compat 和 sync replica。入口设计见：
+> `/mnt/Data1T/mnote/design/02-convex-rust-long-term-architecture/done/2-2-local-first-workspace-convex-control-plane-v1.md`
 >
 > 状态口径以当前仓库真实代码为准：
 > - `[done]`：对应阶段或收口目标已经在当前主线代码中成立