fix(ios): stop miniaudio from clobbering AVAudioSession (stereo->A2DP output death)

The real root cause of "selecting Stereo Mic kills headphone/A2DP output on Join
Voice." Every prior fix worked on the Swift IOSAudioRouter under the false premise
that "miniaudio does NOT touch AVAudioSession on iOS." It does: the core opened
devices via ma_device_init(nullptr, ...), and with a NULL context miniaudio 0.11.25
runs an iOS "hack" that sets the session category by device type, then
ma_context_init__coreaudio calls setCategory()+setActive() on every device open --
capture -> AVAudioSessionCategoryRecord with zero options. That wipes the
.playAndRecord category, the mode, and .allowBluetoothA2DP / .mixWithOthers /
.allowAirPlay that IOSAudioRouter had just configured, killing headphone/A2DP (and
even wired) output. Stereo presets break worst because they rely on the A2DP output
route the wipe removes. TeamTalk avoids this by opening RemoteIO/VPIO AudioUnits
directly and leaving the session entirely to the app.

Fix (core, cross-platform safe): AudioEngine now owns a ma_context built by
make_context_config() with coreaudio.sessionCategory = ma_ios_session_category_none
and noAudioSessionActivate/Deactivate = MA_TRUE, and routes all ma_device_init calls
(playback, capture, loopback) plus enumerate_devices through it. miniaudio no longer
touches AVAudioSession; IOSAudioRouter is the sole owner (the session is already
activated on connect in AppState before any device opens). Context is lazily inited
in start(), reused across restarts, uninited in ~AudioEngine.

Adds TEMP AudioSessionManager.logSessionState() diagnostics (after activate, on route
change, on .streamStarted) to verify on-device that the category stays
PlayAndRecord+allowBluetoothA2DP instead of flipping to Record. Remove once confirmed.

Windows: cmake --build --preset dev clean; ctest --preset dev 21/21.
iOS build + on-device verification pending on Mac.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

clients/apple/iOS/VoiceCatiOS/AudioSessionManager.swift

@@ -62,6 +62,7 @@ final class AudioSessionManager {
         let outputNames = route.outputs.map { $0.portName }.joined(separator: ", ")
         let inputNames = route.inputs.map { $0.portName }.joined(separator: ", ")
         logger.info("session activated — outputs: [\(outputNames)], inputs: [\(inputNames)]")
+        logSessionState("after activate")
     }
 
     /// Deactivate the AVAudioSession. Call ONLY when disconnecting from the server — not
@@ -77,6 +78,34 @@ final class AudioSessionManager {
         logger.info("session deactivated")
     }
 
+    /// TEMP DIAGNOSTIC (stereo-A2DP fix verification): log the full AVAudioSession state —
+    /// category, mode, options, and active route. The bug was miniaudio resetting the category
+    /// to `Record` (no output) on device open; with the core's ma_context now configured to
+    /// leave the session alone, this should report `AVAudioSessionCategoryPlayAndRecord` with
+    /// `allowBluetoothA2DP` set, and the output route should be the headphones/A2DP device —
+    /// even after the mic engine starts. Remove once verified on-device.
+    func logSessionState(_ when: String) {
+        let s = AVAudioSession.sharedInstance()
+        var opts: [String] = []
+        let o = s.categoryOptions
+        if o.contains(.mixWithOthers)      { opts.append("mixWithOthers") }
+        if o.contains(.duckOthers)         { opts.append("duckOthers") }
+        if o.contains(.allowBluetoothHFP)  { opts.append("allowBluetoothHFP") }
+        if o.contains(.allowBluetoothA2DP) { opts.append("allowBluetoothA2DP") }
+        if o.contains(.allowAirPlay)       { opts.append("allowAirPlay") }
+        if o.contains(.defaultToSpeaker)   { opts.append("defaultToSpeaker") }
+        let outs = s.currentRoute.outputs.map { "\($0.portName)[\($0.portType.rawValue)]" }
+            .joined(separator: ", ")
+        let ins = s.currentRoute.inputs.map { "\($0.portName)[\($0.portType.rawValue)]" }
+            .joined(separator: ", ")
+        logger.info("""
+            [SESSION @ \(when, privacy: .public)] category=\(s.category.rawValue, privacy: .public) \
+            mode=\(s.mode.rawValue, privacy: .public) options=[\(opts.joined(separator: ","), privacy: .public)] \
+            inputs=[\(ins, privacy: .public)] outputs=[\(outs, privacy: .public)] \
+            inputCh=\(s.inputNumberOfChannels) outputCh=\(s.outputNumberOfChannels)
+            """)
+    }
+
     @objc private func handleInterruption(_ notification: Notification) {
         guard let info = notification.userInfo,
               let typeValue = info[AVAudioSessionInterruptionTypeKey] as? UInt,
@@ -133,6 +162,7 @@ final class AudioSessionManager {
 
         IOSAudioRouter.shared.refreshRoutes()
         NotificationCenter.default.post(name: .voiceCatDeviceListChanged, object: nil)
+        logSessionState("route change (\(reasonLabel(reason)))")
     }
 
     private func reasonLabel(_ reason: AVAudioSession.RouteChangeReason) -> String {

clients/apple/iOS/VoiceCatiOS/IOSAudioRouter.swift

@@ -6,8 +6,14 @@ private let logger = Logger(subsystem: "cat.voice.VoiceCatiOS", category: "IOSAu
 
 /// iOS audio routing layer — drives all iOS audio route selection via `AVAudioSession`
 /// *before* the core (miniaudio) opens its device. miniaudio does NOT touch
-/// `AVAudioSession` on iOS; it opens the current default route via CoreAudio and that's
-/// it. All iOS audio routing (input port selection, mic orientation/polar patterns,
+/// `AVAudioSession` on iOS — but ONLY because the core deliberately opens its devices
+/// through a `ma_context` configured with `sessionCategory = none` +
+/// `noAudioSessionActivate/Deactivate` (see `AudioEngine::make_context_config` in
+/// `core/src/audio/audio_engine.cpp`). With miniaudio's default NULL-context path it WOULD
+/// reset the category to `Record`/`Playback` with no options on every device open, wiping
+/// `.allowBluetoothA2DP`/`.playAndRecord` and killing headphone/A2DP output (the long-standing
+/// "stereo mic kills output" bug). With that disabled, this class is the sole owner of the
+/// session. All iOS audio routing (input port selection, mic orientation/polar patterns,
 /// HFP vs A2DP, measurement/raw mode, stereo capture) must be driven from here.
 ///
 /// The three user-facing choices:

clients/apple/iOS/VoiceCatiOS/SessionState.swift

@@ -110,6 +110,9 @@ final class SessionState {
                     addActivity("Audio session activate failed: \(error)")
                 }
             }
+            // TEMP DIAGNOSTIC: the core opens its miniaudio devices around now — log the
+            // session state to confirm miniaudio is no longer resetting the category to Record.
+            AudioSessionManager.shared.logSessionState("stream started (user \(ev.userId))")
             addActivity("Stream started (user \(ev.userId))")
         case .streamStopped:
             addActivity("Stream stopped (user \(ev.userId))")