Device checks

Phase 0 verification, and the way through to the Phase 1 spike. Reached from the avatar on Today. Open it from the Home Screen icon rather than Safari — the whole point is that standalone behaves differently.

Inline video

This should be playing, silently, right here — not filling the screen in a player of its own. If it took over the screen, `playsinline` is not doing its job and the session screen’s demo would do the same.