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>

simulator/app.py

@@ -23,7 +23,8 @@ from player.alteration import (
 )
 from player.content import resolve_content
 from player.controls import CONTENT_POSITIONS
-from simulator.clips import load_manifest
+from player.ring import advance_ring
+from simulator.clips import load_manifest, load_ring, ring_move_to_dict, ring_to_dict
 
 STATIC_DIR = Path(__file__).parent / "static"
 MEDIA_DIR = Path(__file__).parent / "sample_media"
@@ -51,6 +52,11 @@ class AlterationRequest(BaseModel):
     calibration: Optional[CalibrationModel] = None
 
 
+class RingAdvanceRequest(BaseModel):
+    from_index: int = 0
+    delta: int
+
+
 def _load_clips(manifest_path: Optional[Path]):
     path = Path(manifest_path) if manifest_path else DEFAULT_MANIFEST
     if path.exists():
@@ -58,9 +64,17 @@ def _load_clips(manifest_path: Optional[Path]):
     return []
 
 
+def _load_ring(manifest_path: Optional[Path]):
+    path = Path(manifest_path) if manifest_path else DEFAULT_MANIFEST
+    if path.exists():
+        return load_ring(path)
+    return None
+
+
 def create_app(manifest_path: Optional[Path] = None) -> FastAPI:
     app = FastAPI(title="HEF Alteration Simulator")
     app.state.clips = _load_clips(manifest_path)
+    app.state.ring = _load_ring(manifest_path)
 
     @app.post("/api/alteration")
     def api_alteration(req: AlterationRequest):
@@ -88,6 +102,19 @@ def create_app(manifest_path: Optional[Path] = None) -> FastAPI:
     def api_clips():
         return {"clips": [c.to_dict() for c in app.state.clips]}
 
+    @app.get("/api/ring")
+    def api_ring():
+        if app.state.ring is None:
+            raise HTTPException(status_code=404, detail="no scale ring in manifest")
+        return ring_to_dict(app.state.ring, app.state.clips)
+
+    @app.post("/api/ring/advance")
+    def api_ring_advance(req: RingAdvanceRequest):
+        if app.state.ring is None:
+            raise HTTPException(status_code=404, detail="no scale ring in manifest")
+        move = advance_ring(app.state.ring, req.from_index, req.delta)
+        return ring_move_to_dict(move, app.state.ring)
+
     if MEDIA_DIR.exists():
         app.mount("/media", StaticFiles(directory=MEDIA_DIR), name="media")
     if STATIC_DIR.exists():