fix(mobile): properly pause and resume other audio during recording

js/mobile/src/lib/recording-audio-session.ts

@@ -0,0 +1,24 @@
+import { setAudioModeAsync, setIsAudioActiveAsync } from "expo-audio";
+
+// Around camera/mic recording we switch the iOS audio session to playAndRecord
+// with `doNotMix`, which cleanly interrupts other apps' audio (Spotify, Apple
+// Music, podcasts). On release we restore a mixable mode and then *deactivate*
+// the session — the deactivation is what passes notifyOthersOnDeactivation to
+// AVAudioSession, which is the signal that lets the previously-playing app
+// auto-resume. Just changing the category is not enough.
+export async function acquireRecordingAudioSession() {
+  await setAudioModeAsync({
+    allowsRecording: true,
+    playsInSilentMode: true,
+    interruptionMode: "doNotMix",
+  });
+}
+
+export async function releaseRecordingAudioSession() {
+  await setAudioModeAsync({
+    allowsRecording: false,
+    playsInSilentMode: true,
+    interruptionMode: "mixWithOthers",
+  });
+  await setIsAudioActiveAsync(false);
+}