docs: FR-CAP-7 microphone capture + mixer contract

docs/01-requirements.md

@@ -16,6 +16,7 @@ Each requirement has a stable ID used across the roadmap, tests, and commits. Pr
 | FR-CAP-4 | M | 1 | Show an unambiguous "recording active" indicator (in-app banner + tray icon). |
 | FR-CAP-5 | S | 7 | Render a live input waveform / level meter while recording. |
 | FR-CAP-6 | S | 7 | Handle audio device changes mid-recording without losing the session. |
+| FR-CAP-7 | S | 1 | Optionally capture the user's **microphone** alongside loopback and mix it into the live transcript (default ON, local-only/no egress, selectable device + "off"). |
 
 ### Recording retention & consent (REC) — see ADR-0009
 

docs/02-architecture.md

@@ -55,7 +55,7 @@ touches files, DB, or network directly — only Tauri commands/events (`04-api-c
 
 | Service | Responsibility | Primary crate(s) |
 |---|---|---|
-| `audio` | WASAPI loopback capture; PCM ring buffer; write WAV to disk; pause/resume | `wasapi`, `hound` |
+| `audio` | WASAPI loopback capture (+ optional microphone, mixed into the transcript stream, FR-CAP-7); PCM ring buffer; write WAV to disk; pause/resume | `wasapi`, `hound` |
 | `hardware` | Enumerate NPU/GPU/CPU; rank backends; report capabilities | `ort`, DXGI via `windows` |
 | `transcription` | Load model on a backend; stream segments (whisper.cpp) or NPU (ONNX) | `whisper-rs`, `ort` |
 | `diarization` | Post-process audio → speaker spans; align to segments; merge | `sherpa-onnx` (FFI) |

docs/04-api-contracts.md

@@ -154,10 +154,15 @@ indicative (async where I/O-bound).
 pub trait AudioCapture: Send + Sync {
     /// Begin WASAPI loopback capture, writing PCM to `wav_path`; frames also pushed to `sink`.
     fn start(&self, wav_path: &Path, sink: FrameSink) -> Result<CaptureHandle, AudioError>;
+    /// Capture the user's microphone (FR-CAP-7); frames pushed to `sink`, no WAV.
+    fn start_microphone(&self, device_id: Option<&str>, sink: FrameSink) -> Result<CaptureHandle, AudioError>;
     fn pause(&self, h: &CaptureHandle) -> Result<(), AudioError>;
     fn resume(&self, h: &CaptureHandle) -> Result<(), AudioError>;
     fn stop(&self, h: CaptureHandle) -> Result<CaptureSummary, AudioError>;
 }
+// When the mic is enabled, `spawn_mixer` sums the loopback + mic 16kHz-mono
+// frames into the single transcription stream (`list_input_devices` enumerates
+// mic devices, mirroring `list_audio_devices` for render devices).
 
 // hardware/mod.rs
 pub trait HardwareDetector: Send + Sync {