Document engineering learnings and refresh handoff guidance

docs/DEPLOYMENT.md

@@ -1,5 +1,9 @@
 # NAS deployment — 2026-09-08
 
+Historical deployment record, not a current health assertion. The iOS music player
+was removed September 12; the media/AAC details below concern the retained backend,
+not a current iOS feature. Reinspect server state before making deployment changes.
+
 The `voice` container on `192.168.86.2` hosts LiveKit, the voice agent,
 token service, music API and nginx. The app connects to
 `https://192.168.86.2:9178`. Docker uses host networking and an
@@ -34,5 +38,7 @@ containers or the music library; it does not include iOS AAC conversion.
 `scripts/deploy-backend.sh` records the launch configuration and refuses to
 replace an existing `voice` container. Run it on the NAS only after building
 the named image and explicitly handling the existing container. It reads
-credentials on the NAS and never prints them. No source changes were pushed;
-future CI deployments must include the compatibility patch to preserve it.
+credentials on the NAS and never prints them. The backend compatibility source was
+not pushed during that deployment; recheck the sibling repository before acting.
+An iOS push does not publish it. Future backend CI deployments must include the
+compatibility patch to preserve it.