Phase 1: dual-track audio capture → mixed-mono 16 kHz WAV + mic VAD

AudioRecorder captures system audio (ScreenCaptureKit) + mic (AVAudioEngine) on a
single serial ioQueue, one shared monotonic t0, time-driven writers (pad gaps /
trim overlaps) so tracks stay aligned, and an energy mic-VAD for 'self' spans.
AudioMixer sums the aligned tracks into mixed_mono_16k.wav. SessionController
drives a serialized start/stop state machine, writes the session folder +
self_vad.json, exposes live level meters, and finalizes on quit.

Hardening from review: ioQueue single-domain (no races), stop() never hangs
(mic-first teardown + bounded stopCapture), layout-agnostic mic deep-copy,
discard-only video output to keep SCStream alive, VAD lockstep on committed
frames, stable signing team in project.yml, single-instance enforcement.

project.yml

@@ -13,9 +13,11 @@ settings:
     CURRENT_PROJECT_VERSION: "1"
     SWIFT_VERSION: "5.0"
     CODE_SIGN_STYLE: Automatic
-    # Leave the team empty; pick your free personal team in Xcode's
-    # Signing & Capabilities tab on first open (see README).
-    DEVELOPMENT_TEAM: ""
+    # Grant's free personal team (cert OU). Baked in so `xcodegen generate` keeps
+    # a STABLE signing identity across regenerations — macOS ties TCC permission
+    # grants (Mic / Screen Recording / Accessibility) to this identity, so a
+    # stable team is what makes those permissions persist across rebuilds.
+    DEVELOPMENT_TEAM: "BK4Y6CXN35"
 
 targets:
   Ten31Transcripts: