docs(memory): split the output path (ffmpeg, encoder, recording, audio) out of ai.md

Unit 3. Verbatim move of 'FFmpeg locator', 'Live encoder + RTMP push',
'Local recording' and 'Live audio capture' into docs/ai/output.md, grouped as
encoder / recording / audio with a 'Related' footer.

ai.md's stub keeps the decisions that must not be re-litigated or rediscovered:
ffmpeg is bundled (never download/fetch; no-network test), args pure and no -re,
probe order NVENC->QSV->AMF->OpenH264 and never libx264, REC/ON-AIR radio-
exclusive by creator ruling, a modal's falsy result must never fall through into
its side effect, full StopStream teardown on every failure, audio pipe closes
BEFORE the video pump, and honest-by-measurement audio (true dBFS meters,
SpeechLeveler + -1 dBFS limiter, live Func gains).

- ai.md Services row and one 'FFmpeg locator section above' pointer repointed;
  MyMistakes.md dead-Pin entry repointed.
- docs/ai/index.md gains the output.md row.

ai.md 1,558 -> 1,289 lines. No source touched; no push.

docs/ai/index.md

@@ -11,6 +11,7 @@ Read the file whose row matches the task. There is no required reading order.
 |------|--------|-----------|
 | [`frame-pipeline.md`](frame-pipeline.md) | Render budget & measurement (`FrameCadence`, per-element composite timing, scene dump), `SceneCompositor` design + `StripPool`, and `FramePump` from scene snapshot to encoder (pacing, pool/paste caches, backpressure, teardown, health stats) | Touching the compositor, the render loop, per-frame cost, `Services/Encoder/*`, or debugging dropped/juddering frames |
 | [`capture.md`](capture.md) | The locked Background layer (screen/game/window capture, WinRT GraphicsCapture interop), the webcam seam + `CameraManager` sessions, MediaPipe background effects, and the vertical 9:16 tier's per-scene camera placement | Touching any frame source, the Background row, camera acquisition/conflicts, background effects, or vertical-tier camera geometry |
+| [`output.md`](output.md) | The bundled `ffmpeg.exe` and the encoder subprocess (args, probe order, seams), local recording (REC/ON-AIR, filenames, private-broadcast close-out), and the WASAPI capture → filter → mix → named-pipe audio chain (TRAX, sync offset, ducking, limiter) | Touching ffmpeg args/bundling, encoder or recording behaviour, REC/ON-AIR, the audio mix and its meters, or loudness/sync problems |
 
 ## Split-out yet to come