mockTransportEnabled

Demo Mode gate.

Debug builds and Firebase Test Lab get it unconditionally, as before. Release builds get it only after the user performs the hidden-features gesture (five taps on the Settings app-version row) — the same deliberate, process-scoped unlock that reveals the firmware-excluded module screens. That keeps a permanently visible fake radio out of the picker for ordinary users while making Demo Mode genuinely reachable in a shipped build, which is what a Play reviewer with no LoRa hardware needs.

HiddenFeaturesUnlock.unlocked is a hot StateFlow, so no scope is needed to observe it here.