Picture-in-Picture for mobile video playback #37

Part of #52 (Post-v1 upgrade track). Post-v1, not scheduled — do not start before the owning v1 workstream ships unless the epic reprioritizes it.

Outcome

Picture-in-Picture for mobile video playback with correct lifecycle (enter on home/gesture, controls, restore).

Acceptance criteria

• DoD: verify green; recording of enter/exit PiP with playback continuity attached