feat(sidebar): persisted project-level last-activity timestamp

[cnjack]

需求

给 conversation 的 project 加上 last update 时间；删除 conversation 时 project 的时间不变、排序不变。

实现

存储：在 session index 旁新增 projects.json sidecar 文件（project path → last-activity timestamp）。不嵌入 session.json，是因为共享 index 可能被旧版本二进制重写而静默丢掉嵌入字段（桌面 sidecar + CLI 混版场景）；sidecar 文件旧版本完全不碰，天然免疫。

写入时机（均为单调 max，按解析后的 RFC3339 瞬时比较而非字符串——数据混有本地时区偏移与 UTC，字符串比较在跨时区时会出错）：

• 会话创建（addToIndex）→ 用会话 StartTime 触碰 project 时间
• 会话真实活动（UpdateSessionMeta 中 UpdatedAt 变化，即一轮对话开始/结束）→ 同步触碰
• pin/archive/rename 等元数据编辑不触碰（UpdatedAt 本身就不动）
• 删除会话绝不回退 project 时间 → 删除最新的会话不会让 project 在侧栏排序中下沉

API：新增 GET /api/projects 返回 [{path, updated_at}]。

前端：

• session slice 新增 projectTimes；启动时 loadProjects 拉取（与 tasks 并行），采用 per-key 单调 max 合并（避免覆盖 in-flight 的实时触碰）
• task_status WS 事件现在携带 project 路径 + 服务端写入的精确时间戳，前端用服务端值实时触碰（不用浏览器时钟）
• Sidebar project 分组排序优先使用持久化时间戳（缺失时回退到子会话派生值，兼容旧数据），project 头部显示相对时间

验证

• go test -race ./internal/session/ ./internal/web/ 通过；新增生命周期契约测试（含混合时区单调性、legacy 回退、删除/改名 round-trip）与 GET /api/projects handler 测试
• golangci-lint 0 issues；make lint-web 通过
• 沙箱 HOME 端到端验证：删除某 project 最新会话后，projects.json 时间戳不变，侧栏该 project 仍显示原相对时间且排序不变（子会话只剩 10d 旧任务时，project 头仍显示 19h 并保持置顶）

对抗评审

已经过一轮对抗评审（adversarial review），修复了：

1. blocker — RFC3339 混合时区偏移下字符串比较错误（全部改为解析瞬时比较）
2. major — 旧版本二进制重写 index 会丢失嵌入的 projects 字段（改为 sidecar 文件）
3. minor — setProjectTimes 全量替换可能覆盖实时触碰（改为单调 max 合并）
4. minor — WS 事件不携带 project，自动化任务无法实时触碰（task_status 现在携带 project + 服务端时间戳，同时修复浏览器时钟偏差问题）

Summary by CodeRabbit

• New Features

  • Added project-level activity tracking to preserve accurate sidebar ordering across sessions.
  • Project groups now display their latest activity time in the sidebar.
  • Added project listing support for loading project paths and activity timestamps.
  • Live task updates now refresh project activity immediately.
  • Legacy installations without project metadata continue to display an empty project list.

• Bug Fixes

  • Project ordering now handles timestamps consistently across time zones.
  • Deleting sessions no longer causes project activity times to move backward.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 9e24c052-757c-401a-8ef4-13732f5ad78c

📥 Commits

Reviewing files that changed from the base of the PR and between 0cbec24 and 198eb17.

📒 Files selected for processing (12)

• internal/session/index_test.go
• internal/session/session.go
• internal/web/engine.go
• internal/web/projects_test.go
• internal/web/server.go
• internal/web/sessions.go
• web/src/app/store.ts
• web/src/app/wsBridge.ts
• web/src/components/Sidebar.tsx
• web/src/lib/api.ts
• web/src/lib/types.ts
• web/src/lib/ws.ts

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📝 Walkthrough

Walkthrough

Project activity timestamps are persisted in projects.json, exposed through a new HTTP endpoint and task-status WebSocket fields, merged into frontend state, and used to order and annotate sidebar project groups.

Changes

Project activity metadata

Layer / File(s)	Summary
Persist project activity metadata internal/session/session.go, internal/session/index_test.go	Adds atomic projects.json persistence, monotonic RFC3339 timestamp updates, deletion preservation, metadata listing, and lifecycle coverage.
Expose project timestamps internal/web/engine.go, internal/web/sessions.go, internal/web/server.go, internal/web/projects_test.go	Adds project metadata to task-status events and registers GET /api/projects, including legacy and populated response tests.
Merge project activity updates web/src/lib/types.ts, web/src/lib/api.ts, web/src/lib/ws.ts, web/src/app/store.ts, web/src/app/wsBridge.ts	Loads project timestamps over HTTP and applies monotonic updates from HTTP snapshots and WebSocket activity events.
Order and render project activity web/src/components/Sidebar.tsx	Uses persisted timestamps for project ordering and displays relative project activity times with session-activity fallback.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant SessionEngine
  participant WebSocket
  participant WSBridge
  participant SessionStore
  participant Sidebar
  SessionEngine->>WebSocket: task_status with project and updated_at
  WebSocket->>WSBridge: forward task status metadata
  WSBridge->>SessionStore: touchProjectTime(path, updatedAt)
  SessionStore->>Sidebar: updated projectTimes
  Sidebar->>Sidebar: reorder groups and render relative time

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: persisted project-level last-activity timestamps.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/project-last-updated

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