feat(sim+player): scale-ring navigation (endless encoder) + cosmos/abyss scales

Add scale-ring navigation to the simulator per the scales-library design §3:
an endless rotary-encoder control (relative, vs the absolute 0-4 experience
knobs) walks a closed ring of neutral "scales of nature" clips, with placeholder
AI zoom/warp transitions between adjacent scales and a small->large wrap (the
infinite-zoom payoff).

- player/ring.py (new, canonical pure logic): ScaleRing + advance_ring; one
  transition clip per edge, played forward zooming inward / reversed outward;
  modulo wrap both ways; chained steps for a multi-detent spin. Mirrors
  player/content.py conventions (frozen dataclasses, pure functions).
- simulator: load_ring + ring_to_dict/ring_move_to_dict; GET /api/ring and
  POST /api/ring/advance (Python owns step/wrap/transition math; the browser
  only plays the returned transition(s) then settles on the target scale).
- frontend: endless-encoder control (zoom in/out buttons + stage scroll),
  current-scale readout, multi-clip active-scale selection, transition playback.
- media: two cheap true-PD scales so the ring is demonstrable -- cosmos
  (NASA/Hubble) + abyss (NOAA Ocean Exploration), provenance recorded in the
  manifest, bytes generated as labelled placeholders by setup_scales_media.py.
  The expensive multi-strength flow-stabilized Right re-bake is DEFERRED (new
  scales carry a raw base only) until the ring is liked; Pi renderer +
  serial/firmware remain deferred (simulator-first).
- docs: ROADMAP slice-3 done; USER_GUIDE scale-ring gesture; plan doc.

Verified: pytest 215 passed / 2 skipped (+22 new); sim boots, /api/ring +
/api/ring/advance correct incl. wrap, media served, and a headless-Chrome CDP
drive walked cosmos -> forest -> abyss -> (wrap) -> cosmos with the active clip
reloading correctly.

Spec: docs/superpowers/specs/2026-06-07-scales-library-and-right-axis-pipeline-design.md (§3)
Plan: docs/superpowers/plans/2026-06-07-scale-ring-navigation.md

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

docs/ROADMAP.md

@@ -139,6 +139,23 @@ Design:
 plan:
 [`2026-06-07-reconciled-simulator-alteration-slice.md`](./superpowers/plans/2026-06-07-reconciled-simulator-alteration-slice.md).
 
+**Slice 3 — scale-ring navigation (simulator) ✅ Done.** Merged to `main`
+(session 0011). Adds the **endless rotary-encoder** control — *relative* (vs the
+absolute 0–4 experience knobs) — that walks a **closed ring** of neutral
+"scales of nature" clips, with placeholder AI zoom/warp **transitions** between
+adjacent scales and a small→large **wrap** (the infinite-zoom payoff, scales
+design §3). The navigation math is canonical Python (`player/ring.py`:
+`ScaleRing` + `advance_ring`, one transition clip per edge, played forward
+inward / reversed outward); the sim exposes `GET /api/ring` + `POST
+/api/ring/advance` and the browser only plays the returned transition(s) then
+settles on the target scale, keeping the live knob alteration on top. Two cheap
+**true-PD** scales were added so the ring is demonstrable — `cosmos` (NASA/Hubble)
+and `abyss` (NOAA Ocean Exploration), provenance recorded in the manifest, bytes
+generated as labelled placeholders by `simulator/setup_scales_media.py`. The
+expensive real multi-strength flow-stabilized Right re-bake is **deferred** (new
+scales carry a raw base only) until the ring is liked. Plan:
+[`2026-06-07-scale-ring-navigation.md`](./superpowers/plans/2026-06-07-scale-ring-navigation.md).
+
 **Remaining slices (not started):**
 
 - **Runtime renderer** — drive the single panoramic projector via mpv/ffmpeg;
@@ -152,10 +169,9 @@ plan:
 - **Offline v2v variant pipeline** — author the pre-baked Right restyle variants
   via the local flow-stabilized SD pipeline (now ~free, not a paid API — see the
   scales-library/right-axis design §1/§4); a real multi-strength flow-stabilized
-  re-bake per base clip + the multilingual label/string tables + TTS.
-- **Scale-ring navigation** — the endless rotary encoder + short pre-baked AI
-  zoom/warp transitions between neutral "scales of nature" clips on a closed ring
-  (scales-library design §3); a new control + offline pipeline element.
+  re-bake per base clip + the multilingual label/string tables + TTS. The
+  **scale-ring transitions** (forward/reverse per-edge morphs) are part of this
+  offline pipeline too — the simulator currently uses placeholders.
 - **Catalog model changes** — audio *source* + "neutral base" vs "altered
   variant" flag (sub-project 2 territory, design §13).