fix(macos): scrub parent-session env, survive node upgrades and reboots, store lanes by real path (#22)

What broke (code audit, untested on a Mac):
- Without systemd the server is always spawned from inside a Claude Code
  session, so it inherited CLAUDECODE, CLAUDE_CODE_SESSION_ID,
  CLAUDE_PLUGIN_ROOT, ... and tmux handed them to every lane pane (a codex
  pane even resolved as `claude` in `agenthub`'s harness check).
- The ~/.local/bin/agenthub launcher pinned a versioned node path that
  `brew upgrade`/nvm deletes, leaving the CLI dead until the next bootstrap.
- A discovery entry left over from before a reboot could name a recycled pid,
  so the bootstrap's fast path believed a dashboard was live and
  stopDashboard could signal an unrelated process.
- Lanes were stored under the typed cwd; macOS reports /private/tmp and the
  on-disk case, so sessions never bound to a /tmp or differently-cased lane.

What changed:
- server/index.js deletes a DENYLIST of parent-session variables at startup;
  user config (CLAUDE_CONFIG_DIR, CLAUDE_CODE_USE_BEDROCK, ANTHROPIC_*) stays.
- linkCli's launcher falls back to `node` on PATH when the pinned one is gone.
- liveServers ignores entries whose startedAt predates this boot (60 s margin).
- createLane and POST /api/lanes/ensure store/look up fs.realpathSync.native
  of an existing cwd; the liveness reaper also tries the realpath. Existing
  rows are untouched.
- session-liveness gains an exec seam so the darwin ps+lsof branch is tested.
- plugin-doctor names ~/.zshrc on darwin; INSTALL.md gains a macOS section
  with the Mac verification checklist, mirrored in both READMEs and PLUGINS.md.
No launchd, no macOptionIsMeta, engines stays >=20.

README.vi.md

@@ -92,6 +92,12 @@ sudo pacman -S tmux          # Arch
 
 Windows không có tmux native — chạy AgentHub trong WSL2 và cài tmux ở trong đó.
 
+macOS (đã rà soát code, chưa kiểm thử trên máy Mac): `brew install node git tmux`
+(Node >= 22.5 cho bản plugin), thêm `~/.local/bin` vào `PATH` trong `~/.zshrc`.
+Không có systemd, nên dashboard chạy đến khi đăng xuất/khởi động lại và tự lên
+lại ở phiên Claude Code kế tiếp, hoặc chạy tay bằng `agenthub start`. Chi tiết
+và checklist kiểm tra: [INSTALL.md § macOS](INSTALL.md#macos).
+
 Kiểm tra, cả từ shell của bạn lẫn từ góc nhìn của server:
 
 ```bash