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>

INSTALL.md

@@ -2,6 +2,27 @@
 
 A step-by-step guide to get the Claude Code Agent Monitor up and running on your machine, with optional sections for importing history, running in a container, and using the native desktop app (macOS & Windows).
 
+## Fastest path — install it as a Claude Code plugin
+
+If all you want is a working dashboard, skip every step below. From Claude Code:
+
+```
+/plugin marketplace add Smartgift-AI/Claude-Code-Monitor
+/plugin install ccam@claude-code-agent-monitor-plugins
+```
+
+The next session start installs the hooks, boots the server, puts the `ccam` CLI
+on PATH and connects the MCP tools — no clone, no `npm run setup`, no
+`npm run install-hooks`, no manual `npm start`. Run `/ccam-doctor` to check the
+result and `/ccam-open` to build the UI and get the URL.
+
+Requires Node **>= 22.5** (a plugin install has no native `better-sqlite3`, so
+the server stores data through `node:sqlite`). Full behavior, including the
+uninstall cleanup, is in [`docs/PLUGINS.md`](docs/PLUGINS.md).
+
+Follow the steps below instead when you want a checkout — to develop the
+dashboard, run it from source, or stay on Node 20.
+
 ## Requirements
 
 | Requirement | Version | Notes |