fix(plugin): restart a server left on a retired plugin root

A plugin update applied mid-session (/plugin followed by /reload-plugins)
fires no SessionStart, so the bootstrap's version handover never runs and the
dashboard server keeps executing a cache directory Claude Code has already
discarded. /ccam-open then rebuilt the bundle from the new root against that
old server, and the new bundle called routes the old server never had:
/api/lanes/pipeline-stats fell through to /:id and rendered "lane not found",
/api/workflows/skill-usage fell through to the SPA catch-all and broke
JSON.parse on the returned HTML. Both Workflows panels showed an error while
the code they needed was sitting on disk.

plugin-open now re-runs bootstrap when the live server's recorded pluginRoot
differs from the current one, or when no server is live at all. Bootstrap
already owns the stop/start and the dependency install the new root may need,
so this only restores the trigger that a mid-session update skips.

plugins/ccam/commands/ccam-open.md

@@ -12,8 +12,12 @@ node "${CLAUDE_PLUGIN_ROOT}/scripts/plugin-open.js" --force
 ```
 
 Install + build takes a few minutes if the client toolchain isn't already
-installed; otherwise the rebuild itself takes ~10-15s. No server restart is
-needed — the server already serves from that directory.
+installed; otherwise the rebuild itself takes ~10-15s. The server serves from
+that directory, so it usually needs no restart — but if it is down, or still
+running from a plugin root a mid-session `/plugin` update retired, the command
+re-runs bootstrap first and prints `Server restarted on the current plugin
+version.` (without it, the fresh bundle would call routes that old server
+never had).
 
 Then help the user open it: