feat(update): make /ccam-update pull the latest ccam plugin version, not just rebuild the current one

Docs and the command's own instructions previously implied /ccam-update
fetches new code; it only reinstalled deps and restarted the server
against whatever version was already resolved. It now also runs
`claude plugin marketplace update` + `claude plugin update ccam@<mp> -y`
first, and says plainly that /reload-plugins is still a manual step
(no CLI/script equivalent exists to apply it automatically).

docs/PLUGINS.md

@@ -129,7 +129,7 @@ output goes to `client-build.log` next to it; the server's own output goes to
 | Command | Does |
 |---|---|
 | `/ccam-doctor` | Node version, bootstrap state, runtime deps, server liveness, duplicate hooks, CLI launcher + PATH, MCP build freshness, UI bundle |
-| `/ccam-update` | Reinstall dependencies and restart the server against the current plugin version (`plugin-bootstrap.js --force`) |
+| `/ccam-update` | Pull the latest `ccam` release via `claude plugin marketplace update` + `claude plugin update ccam@<marketplace> -y`, then reinstall dependencies and restart the server (`plugin-bootstrap.js --force`). The plugin pull needs a manual `/reload-plugins` afterward to take effect in the current session — not scriptable from a command. |
 | `/ccam-open` | Build the UI bundle if missing, then print the dashboard URL |
 
 ### Where things live