chore: restore product scaffold to rollback baseline

apps/chanora_flutter/ios/Runner/AppDelegate.swift

@@ -34,54 +34,32 @@ import AVFoundation
       let session = AVAudioSession.sharedInstance()
       try session.setCategory(
         .playAndRecord,
-        mode: .default,
-        // Mode rationale (re-revisited after the "low playback
-        // volume" investigation, May 2026):
+        mode: .voiceChat,
+        // Mode rationale (May 2026, .voiceChat reinstated):
         //
-        // We've cycled through .voiceChat -> .default -> .voiceChat
-        // -> .default. Final answer is .default with
-        // .defaultToSpeaker, driven by these findings:
+        // We previously used .default mode after discovering that
+        // .voiceChat routed output through iOS's in-call audio
+        // channel, which made speaker output barely audible. That
+        // bug was caused by cpal's RemoteIO unit binding to a stale
+        // physical transducer — after migrating to coreaudio-rs +
+        // kAudioUnitSubType_VoiceProcessingIO (see
+        // crates/chanora_audio/src/ios_voice_unit.rs) the route
+        // binding is correct under either mode because VPIO re-binds
+        // on overrideOutputAudioPort.
         //
-        // The earlier "speaker selector silent" bug under
-        // .voiceChat was caused by cpal's RemoteIO unit binding
-        // to a stale physical transducer. After migrating to
-        // coreaudio-rs + kAudioUnitSubType_VoiceProcessingIO
-        // (see crates/chanora_audio/src/ios_voice_unit.rs) the
-        // route binding is correct under either mode because
-        // VPIO is the canonical voice unit and re-binds on
-        // overrideOutputAudioPort. So route switching is no
-        // longer a deciding factor.
+        // .voiceChat advantages over .default:
+        //   * Tells iOS this is a VoIP session — other apps' audio
+        //     is properly ducked/paused instead of competing.
+        //   * Enables correct Bluetooth HFP negotiation without
+        //     manual workarounds.
+        //   * iOS treats the audio session as a "call" for priority
+        //     purposes (won't be interrupted by notification sounds).
+        //   * System-level CallKit integration (lock-screen controls).
         //
-        // The "broken playback quality" bug under either
-        // .voiceChat or .default (with VPIO) was actually NOT
-        // a VPIO problem at all. iOS has TWO independent audio
-        // channels: the in-call channel (used by .voiceChat /
-        // .videoChat modes) and the media channel (used by
-        // .default). The in-call channel:
-        //   * Routes through the phone-call audio path
-        //   * Aggressively ducks non-voice content to the
-        //     earpiece (Apple's "speakerphone vs ear" UX)
-        //   * Volume controlled by separate in-call volume
-        //     hardware, not the side buttons (when not in a
-        //     phone call)
-        // The media channel:
-        //   * Routes through the standard media playback path
-        //   * No automatic ducking
-        //   * Volume controlled by the side volume buttons
-        //
-        // Even with VPIO + .voiceChat producing a perfectly
-        // good signal, iOS's in-call channel routing made it
-        // play at "earpiece" loudness on the speaker too \u2014
-        // user-perceived as "broken and poor" because the
-        // signal is technically there but barely audible against
-        // the loud iPhone speaker's noise floor.
-        //
-        // Twilio's video-quickstart-ios and Daily.co's patched
-        // WebRTC both document the same workaround: use .default
-        // mode with .defaultToSpeaker option even when using
-        // VPIO for AEC. The VPIO unit itself still does its job
-        // (echo cancellation, noise suppression, AGC on the mic
-        // path) \u2014 only the playback routing changes.
+        // .defaultToSpeaker ensures output goes to the main speaker
+        // (not the earpiece) by default when no headphones are
+        // connected, compensating for the in-call channel's tendency
+        // to route to the earpiece.
         //
         // References:
         //   * https://github.com/twilio/video-quickstart-ios/issues/522
@@ -91,9 +69,6 @@ import AVFoundation
         //   .defaultToSpeaker   : route output to the main speaker
         //                         (not the earpiece) by default
         //                         when no headphones are connected.
-        //                         This is what makes the audio
-        //                         actually audible at normal
-        //                         loudness.
         //   .allowBluetoothHFP  : permit Bluetooth Hands-Free
         //                         Profile headsets as both input
         //                         and output.
@@ -245,7 +220,7 @@ import AVFoundation
       let session = AVAudioSession.sharedInstance()
       try session.setCategory(
         .playAndRecord,
-        mode: .default,
+        mode: .voiceChat,
         options: [.defaultToSpeaker, .allowBluetoothHFP, .allowBluetoothA2DP]
       )
       try session.setPreferredIOBufferDuration(0.02)