docs(audio): reframe control-surface spec content->visual+audio; record §12 decisions + roadmap

- networked-control-surface §3/§4/§5/§6: Content -> Visual + Audio; transitions.content
  -> transitions.visual; render.content -> render.video + render.audio; SSE notes
- audio spec §12: resolved (audio=live ~0.6s; noise=pink; tap-to-start overlay);
  status -> in implementation
- ROADMAP: session-0020 audio increment; music layer deferred

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/ROADMAP.md

@@ -196,8 +196,23 @@ every transition, so fast navigation stays responsive on placeholder media.
     browser. Real strict-PD bases for all five scales sourced per
     [`docs/content-sourcing.md`](./content-sourcing.md).
 
+  - **Audio + separated Visual/Audio controls (session 0020) ✅ Done.** The
+    simulator now has **sound**: per-altitude soundtracks that follow the Altitude
+    dial + a synthesized pink **white-noise** bed, behind two orthogonal controls —
+    **Visual** (on/off) × **Audio** (off / soundtrack / white_noise) — replacing
+    the bundled 7-way Content dial. `tools/pipeline/audio_ops` + `audio_run` +
+    `simulator/build_audio_media.py` (ffmpeg loop/loudnorm/noise, gitignored
+    assets), `Scale.audio` in the manifest, a pure `player/audio.py` resolver
+    (retiring `player/content.py`), server-resolved `render.audio.url`, and a client
+    A/B `<audio>` crossfade layer. This is the "Content step" of the future control
+    surface (it reframes the proposed networked-control-surface spec §3/§5). Spec:
+    [`2026-06-26-audio-video-separated-controls-design.md`](./superpowers/specs/2026-06-26-audio-video-separated-controls-design.md);
+    plan:
+    [`2026-06-26-audio-video-separated-controls.md`](./superpowers/plans/2026-06-26-audio-video-separated-controls.md).
+
   - **Still deferred:** real **i2v ring transitions** (need a generative-video
-    model + adjacent real bases); Pi renderer + serial/firmware.
+    model + adjacent real bases); Pi renderer + serial/firmware; the **music**
+    audio layer (reserved dial position, no assets yet).
 - **Catalog model changes** — audio *source* + "neutral base" vs "altered
   variant" flag (sub-project 2 territory, design §13).