Nightly update: cartridge discovery stays in sync

This nightly is mostly about making cartridge installs, failures, and removals show up more accurately in the macOS app.

What changed

Installed cartridges now refresh when discovery state actually changes, instead of waiting on a polling cycle. That makes new installs, removals, and verification failures show up faster in the cartridges UI.
The app is stricter about what counts as an installed website cartridge. Bundled providers no longer leak into the installed cartridges browser, so the website edition's cartridge list is clearer and more accurate.
Cartridge lifecycle and failure state handling is more reliable during install and verification. In-progress and failed installs are surfaced more consistently instead of being overwritten by stale runtime snapshots.
The bundled text cartridge and related registry metadata were cleaned up so build-time registry identity is handled more consistently across the app, engine, and cartridges.
A few smaller rough edges were also addressed:
- quitting during early startup still exits immediately
- startup tips remain trimmed down
- the downloads page behaves better on mobile and keeps included cartridge panels from stacking open

This is a nightly build intended for testing and feedback.
Most of the work in this build is around cartridge discovery, packaging boundaries, and state synchronization rather than major new end-user features.