The store snapshotted `AppState.currentState` at module load and only
tracked transitions delivered to its listener. A background transition
that happened before the first consumer mounted (cold launch to the app
switcher, deep link landing blurred) left the stored value at "active",
so the first ambient loop could start offscreen.

`subscribeToPlatformSignals` now registers the AppState listener first
and then folds the platform's current value; transitions landing in
between are covered by the listener. Focused tests cover both orderings
with a fresh module instance per case.