Local installs auto-update from the registry

A local (Colima/k3s) install can now stay current without manual updates: memex-local autoroll up --acr makes the existing auto-roll watcher also track the container registry's promoted main tag. Every merge that passes CI rolls into the local portal automatically — the migration runs first, then the portal restarts on the new image, exactly like the cloud portals' self-update.

The same mode keeps the mounted plugin repository on its main branch (only when it is clean and parked there — a working copy with changes is never touched), so Store plugins and modules stay current too. Plain memex-local autoroll up returns to the build-only watcher for the local development loop.