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.

MyMistakes.md

@@ -1227,7 +1227,7 @@ clothes, and the failure mode is invisible because the sentence still *sounds* a
 Corollary: **a stale external fact inside a shipped document is worse than a missing one** — it
 is trusted, acted on, and costed. When a doc makes a factual claim about the outside world
 (certificates, platform behaviour, policy text), re-verify it on touch, not on memory. This is
-the same class as the dead-Pin incident in `FfmpegLocator` (`ai.md` → FFmpeg locator): an
+the same class as the dead-Pin incident in `FfmpegLocator` ([`docs/ai/output.md`](docs/ai/output.md) → FFmpeg locator): an
 external thing changed, our record of it did not, and the mismatch was discovered by a user
 rather than by a test. **Records of the outside world rot silently and are believed until they
 cost money.**