perf: lighter, louder local install — vendored ReDoc, bootstrap failures shown in the session

- Plugin bootstrap: a failed npm install, a Node older than 22.5 or a failed UI
  build is recorded in runtime/last-failure.json; the next SessionStart prints
  it once as a systemMessage naming the log and /agenthub-doctor (a different
  failure is reported again; a successful bootstrap clears it). The foreground
  pass checks the Node version itself and spawns no worker on an old Node.
- ReDoc: the standalone bundle (redoc 2.5.4, MIT, licence files kept) is
  vendored under server/vendor/redoc/ and the `redoc` dependency dropped —
  a runtime install (npm ci --omit=dev --ignore-scripts) goes 126 MB -> 45 MB.
  vendor/ is excluded from the header audit and prettier.
- git missing from PATH: lane git actions answer 503 EGITMISSING with the
  install command instead of a bare ENOENT.
- package.json engines: node >=22.5.0 (node:sqlite), matching MIN_NODE.
- Docs: INSTALL.md is the one install/setup guide (SETUP.md merged in and now a
  pointer); no VS Code extension claim, one client-install hint, no
  windows-build-tools, better-sqlite3 notes scoped to checkouts, new
  "Plugin bootstrap never comes up" troubleshooting entry.

docs/API.md

@@ -1006,6 +1006,9 @@ cannot collide on `index.lock`.
   the file resolves by removing it. `merge-commit` is `409 ECONFLICTS` while
   anything is unmerged, and it and `merge-abort` are `409 ENOMERGE` with no
   merge in progress. `merge-abort` needs `confirm: true` (`400 ECONFIRM`).
+- Any action on a host with no `git` binary (or none on the dashboard's PATH)
+  is `503 EGITMISSING`: a missing dependency, not a bad request; the message
+  carries the install command (like `ETMUXMISSING` for tmux).
 - `push` pushes `HEAD`, never a branch name from the request, so a workspace can
   only push the branch it is on.
 - A **path** in the body is never trusted as a path: `stage`, `unstage` and

docs/OVERVIEW.md

@@ -115,7 +115,7 @@ Internal build — all rights reserved.
 
 | Need | Version | Required for |
 |---|---|---|
-| **Node.js** | >= 20 (>= 22.5 for a plugin install) | Everything. Both suites are verified green on **24** and **26** |
+| **Node.js** | >= 22.5 (`node:sqlite`; Node 20 is end-of-life) | Everything. Both suites are verified green on **24** and **26** |
 | **npm** | 9+ | Ships with Node |
 | **git** | any | Cloning, and every workspace operation (worktrees, branch/status reads) |
 | **tmux** | 3.x | The browser run console, `agenthub workspace shell`, typing `/reload-plugins` into a live pane |

docs/OVERVIEW.vi.md

@@ -81,7 +81,7 @@ Internal build — all rights reserved.
 
 | Cần | Phiên bản | Dùng cho |
 |---|---|---|
-| **Node.js** | >= 20 (>= 22.5 nếu cài qua plugin) | Tất cả. Cả hai test suite verify xanh trên Node **24** và **26** |
+| **Node.js** | >= 22.5 (`node:sqlite`; Node 20 đã hết hạn hỗ trợ) | Tất cả. Cả hai test suite verify xanh trên Node **24** và **26** |
 | **npm** | 9+ | Đi kèm Node |
 | **git** | bất kỳ | Clone repo, và mọi thao tác workspace (worktree, đọc branch/status) |
 | **tmux** | 3.x | Run console trên trình duyệt, `agenthub workspace shell`, gõ `/reload-plugins` vào pane đang sống |

docs/PLUGINS.md

@@ -61,13 +61,13 @@ claude --plugin-dir plugins/agenthub-analytics
 ## Prerequisites
 
 - [Claude Code](https://docs.anthropic.com/en/docs/claude-code) installed and authenticated
-- Node **>= 22.5** when installing via the `agenthub` plugin. A plugin install has no
-  native `better-sqlite3`, so the server stores data through `node:sqlite`, which
-  landed in 22.5. The bootstrap refuses with one line on anything older instead
-  of letting the server crash. (A checkout install still works on Node >= 20.)
+- Node **>= 22.5**. A plugin install has no native `better-sqlite3`, so the
+  server stores data through `node:sqlite`, which landed in 22.5. The bootstrap
+  refuses on anything older instead of letting the server crash, and says so in
+  the session (below). A checkout needs the same (`engines` in `package.json`).
 - The Agent Monitor dashboard reachable at `http://localhost:4820` — the `agenthub`
   plugin starts it for you; a checkout starts it with `npm start` (see
-  [SETUP.md](../SETUP.md))
+  [INSTALL.md](../INSTALL.md))
 
 Skills and commands are invoked as `/agenthub-<plugin>:<name>`. Agents are dispatched automatically by Claude Code (or named explicitly).
 
@@ -124,7 +124,7 @@ waits on an install:
 
 1. **Fast path** — recorded state matches this plugin build and a server is live → exit. "Live" means a discovery entry whose pid answers AND whose `startedAt` is after this boot (60 s margin): an entry left over from before a reboot names a pid the OS may have handed to an unrelated process, and without systemd (macOS) nothing else clears it.
 2. **Superseded check** — if Claude Code records a DIFFERENT build of this plugin as installed, this one logs a line and does nothing else (see [A retired build never acts](#a-retired-build-never-acts)).
-3. **Node gate** — refuse below 22.5 with one line (see Prerequisites).
+3. **Node gate** — refuse below 22.5 with one line (see Prerequisites). Also checked by the foreground pass itself (it costs nothing), which then spawns no worker and tells the session at once.
 4. **Lock** — atomic `mkdir` lock holding the PID; reclaimed when the owner is dead or the lock is older than 10 minutes, so two sessions cannot race the install or spawn two servers.
 5. **Install** — only when the dependencies changed (`depsHash` covers what npm installs — the dependency lists and the lockfile's package tree — never the release's own `version`, so a plain version bump reinstalls nothing): `npm install --omit=dev --ignore-scripts` into the runtime dir, output in `runtime/npm-install.log`, run as the npm bundled with the node running the bootstrap (`npmCommand`: its `npm-cli.js` beside `process.execPath`, no shell, that node's directory first on PATH; `npm` on PATH only when that node ships none) — the update chain runs with the dashboard server's environment, whose PATH need not reach `npm.cmd` on Windows. The UI build below and the doctor's npm row use the same npm (never into the plugin cache, which is garbage-collected and replaced on every update). `--ignore-scripts` keeps the root `postinstall` from pulling the whole Vite client toolchain.
 6. **Legacy hook cleanup** — see above.
@@ -153,6 +153,17 @@ goes to `~/.claude/agenthub/runtime/bootstrap.log`; npm's own output goes to
 `npm-install.log` and the UI build's to `client-build.log` next to it; the server's own output goes to
 `server.log`.
 
+**A failure is reported once, in the session.** The worker's output is
+discarded, so a Node that is too old, a failed npm install or a failed UI build
+is recorded in `runtime/last-failure.json` (kind, message, log file). The NEXT
+foreground pass — its stdout is what Claude Code reads — prints it as a
+SessionStart `{"systemMessage": "AgentHub: … — details in <log>. Run
+/agenthub-doctor …"}` and marks it reported, so the same failure is not repeated
+every session; a different failure is reported again, and a bootstrap that
+succeeds removes the file. The steady state prints nothing, and the report is a
+single small read (plus one write, only when there is something to show) — the
+fast path still spawns nothing.
+
 ### A retired build never acts
 
 `claude plugin update` unpacks the new version into a **new** cache directory

docs/README.md

@@ -9,8 +9,7 @@ Comprehensive documentation for the Agent Dashboard project.
 - [Architecture Overview](../ARCHITECTURE.md) - System design and technical reference
 - [I18N Architecture](./I18N.md) - Internationalization architecture and usage guide
 - [CLI Reference](./CLI.md) - The `agenthub` terminal CLI: every command, discovery, safety model
-- [Setup Guide](../SETUP.md) - Installation and configuration
-- [Installation](../INSTALL.md) - Detailed installation instructions
+- [Installation & setup](../INSTALL.md) - Installation, configuration and troubleshooting
 
 ---
 
@@ -20,7 +19,7 @@ Comprehensive documentation for the Agent Dashboard project.
 
 ```mermaid
 graph TB
-    Start[Start Here] --> Setup[SETUP.md<br/>Installation & Config]
+    Start[Start Here] --> Setup[INSTALL.md<br/>Installation & Config]
     Start --> Architecture[ARCHITECTURE.md<br/>System Design]
     
     Setup --> Client[Client README<br/>React UI docs]
@@ -62,7 +61,7 @@ graph TB
 
 ```mermaid
 graph LR
-    A[New to Project] --> B[Read SETUP.md]
+    A[New to Project] --> B[Read INSTALL.md]
     B --> C[Install Dependencies]
     C --> D[Run npm run dev]
     D --> E[Open localhost:5173]
@@ -75,7 +74,7 @@ graph LR
 
 1. Install the system packages — `node` (20+), `git`, and `tmux` (the run
    console has no fallback without it): [INSTALL.md → Step 0](../INSTALL.md#step-0--system-packages)
-2. Read [SETUP.md](../SETUP.md)
+2. Read the rest of [INSTALL.md](../INSTALL.md)
 3. Run `npm run setup`
 4. Run `npm run dev`
 5. Open browser to `http://localhost:5173`
@@ -287,7 +286,7 @@ graph LR
 **Documentation:**
 - [Hook System Guide](./HOOKS.md)
 - [Hook Processing](../server/README.md#hook-processing)
-- [Installation](../SETUP.md#install-hooks)
+- [Installation](../INSTALL.md#hook-auto-installation)
 
 ---
 
@@ -441,4 +440,4 @@ This documentation covers:
 - ✅ **Internationalization** - Language resources, switching flow, locale formatting, rollout checklist
 - ✅ **Development guides** - Setup, testing, contributing
 
-**Start with:** [SETUP.md](../SETUP.md) for installation, then explore specific areas based on your role.
+**Start with:** [INSTALL.md](../INSTALL.md) for installation, then explore specific areas based on your role.