feat(plugins): make CCAM installable straight from a Claude Code plugin

Adds a root `ccam` plugin (`.claude-plugin/plugin.json`, `"source": "./"`) so
`/plugin marketplace add` + `/plugin install ccam@...` is enough on a machine
with nothing but Claude Code: no clone, no npm run setup, no manual npm start.

- scripts/plugin-bootstrap.js: SessionStart hook. Fast-path exit, Node >=22.5
  gate (node:sqlite), mkdir lock with stale reclaim, deps installed into
  ~/.claude/agent-dashboard/runtime/ (never the plugin cache), legacy
  checkout-hook cleanup (backed up), ~/.local/bin/ccam launcher, eager UI
  build so client routes like /run work immediately, detached server spawn.
- scripts/plugin-open.js, scripts/plugin-doctor.js: /ccam-open, /ccam-doctor.
- server/index.js: DASHBOARD_CLIENT_DIST override (plugin cache is read-only).
- mcp/build/ is committed (plugin MCP servers start before any bootstrap could
  build them) and kept honest by scripts/check-mcp-build.js (content hash,
  not mtime), enforced by pre-commit when mcp/src changes.
- plugins/ccam-dashboard/.mcp.json moved under plugins/ccam/ with a working
  ${CLAUDE_PLUGIN_ROOT} path (the old relative path never resolved from a
  marketplace-cached subdir).
- Docs: README, INSTALL, SETUP, ARCHITECTURE, CLAUDE.md, docs/PLUGINS.md,
  docs/MCP.md, docs/CLI.md, docs/HOOKS.md.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -26,7 +26,25 @@ are verified on — node 25 currently breaks 6 server tests through a
 better-sqlite3 ABI mismatch and 20 client tests through a global `localStorage`
 change.
 
-## Install and run
+## Install as a Claude Code plugin
+
+Two commands on a machine that has nothing but Claude Code, no clone and no
+`npm run setup`:
+
+```
+/plugin marketplace add Smartgift-AI/Claude-Code-Monitor
+/plugin install ccam@claude-code-agent-monitor-plugins
+```
+
+The first session start installs the hooks, boots the server, puts `ccam` on
+PATH and connects the MCP tools; it runs detached, so the session never waits on
+it. `/ccam-doctor` reports the state, `/ccam-open` builds the UI and prints the
+URL, `/ccam-update` refreshes after a plugin update. This path needs Node
+**>= 22.5** (no native `better-sqlite3`, so the server uses `node:sqlite`).
+Details, including what to delete on uninstall:
+[`docs/PLUGINS.md`](docs/PLUGINS.md).
+
+## Install from a checkout
 
 ```bash
 npm run setup          # root, client and vscode-extension dependencies
@@ -42,8 +60,11 @@ Development, with hot reload:
 npm run dev            # server on :4820, Vite client on :5173
 ```
 
-`DASHBOARD_PORT` overrides the port. `postinstall` writes the Claude Code hook
-entries that feed the dashboard.
+`DASHBOARD_PORT` overrides the port, `DASHBOARD_CLIENT_DIST` overrides where the
+built UI is served from (defaults to `client/dist`; the plugin install points it
+at its own runtime directory). `postinstall` writes the Claude Code hook entries
+that feed the dashboard — do not run it when the `ccam` plugin is installed, or
+every event is counted twice.
 
 ## The CLI