feat: stop background audio during recording, resume after

[adithya1012]

Description

Pulse now will handle the background app playing while recording the audio.
Added a local native Expo module (audio-focus) that directly controls the OS-level audio focus on both Android and iOS. A useAudioSession hook integrates it into the recording flow.

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Demo

LINK

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How it works

Android

• requestAudioFocus → AudioManager.requestAudioFocus(AUDIOFOCUS_GAIN_TRANSIENT) — OS signal that causes Spotify/podcasts to pause
• abandonAudioFocus → AudioManager.abandonAudioFocus() — tells Spotify/podcasts they can resume

AUDIOFOCUS_GAIN_TRANSIENT (not AUDIOFOCUS_GAIN) is intentional — transient means Spotify receives AUDIOFOCUS_LOSS_TRANSIENT and automatically resumes when we're done.

Why not expo-audio's setIsAudioActiveAsync?
It is a complete no-op on Android — it only sets an internal flag and never calls requestAudioFocus. Confirmed in AudioModule.kt lines 183–195.

iOS

• requestAudioFocus → AVAudioSession.setActive(true) — activates session, interrupting other apps
• abandonAudioFocus → AVAudioSession.setActive(false, options: .notifyOthersOnDeactivation) — the .notifyOthersOnDeactivation flag is the iOS signal that tells Spotify/Apple Music to resume. Without this flag, they stay paused indefinitely.

setAudioModeAsync (expo-audio) configures the AVAudioSession category (playAndRecord, doNotMix) on both platforms before focus is claimed.

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Files changed

File	Change
audio-focus	New local native Expo module (Kotlin + Swift)
useAudioSession.ts	New hook — activateRecordingSession / deactivateRecordingSession
shorts.tsx	Calls activate on record tap, deactivate on stop and screen unmount
AndroidManifest.xml	Adds MODIFY_AUDIO_SETTINGS permission
.gitignore	Excludes audio-focus Android build output

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Bug fixed during implementation

expo/expo#34025 — passing both interruptionMode (iOS) and interruptionModeAndroid in the same setAudioModeAsync call crashes on Android with a Kotlin enum cast error. Fixed by spreading only the platform-relevant key via Platform.OS.

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Testing

1. Start playing music in Spotify
2. Open the camera screen → music pauses immediately
3. Record a clip → silence throughout
4. Stop recording → Spotify resumes automatically ✅

NOTE: Tested in Android. This need to be tested in iOS.