Venues: song sky, ride roadside, room camera, filmstrip venue pin

- Shared sky dome (src/venues/sky.js): gradient backdrop from palette /
  section light / style texture, wired into chamber/stage/ride with fog
  matched to the dome mid colour — replaces clear-to-black
- Ride roadside: houses, signs, trees, seeded viz billboard, all analytic
  scroll; popMul fade for crew, arrangement-gated roadside (no mid-section
  popping); parked idle creep + engine shake; analytic dash clock
- Room camera: traverse glide + progress look sweep + per-section dolly,
  single-side room visits, one re-hang max; venue framing per archetype
- Filmstrip venue selector (?venueSel=) with cache key; seed persisted to
  URL on reroll; gallery query plumbing

flow-state/src/venues/chamber.js

@@ -7,6 +7,7 @@
 // Primitives only in V1 — no glTF kit.
 
 import { actorToGeometry } from '../actors/meshes.js';
+import { buildSky, paintSky } from './sky.js';
 
 export const chamber = {
     name: 'Chamber',
@@ -212,6 +213,11 @@ export const chamber = {
         scene.fog = new T.Fog(0x0e0e12, 12, 28);
         scene.userData.transparentBackground = true;
 
+        // Song sky above the open room — replaces clear-to-black. Radius 90
+        // clears the 22-unit room with margin; fog melts the horizon.
+        const sky = buildSky(T, { radius: 90 });
+        scene.add(sky.mesh);
+
         // Population container — memories
         const popGroup = new T.Group();
         popGroup.name = 'memories';
@@ -221,6 +227,7 @@ export const chamber = {
             room, floor, floorMat, wallMat, walls, windowMesh, windowMat,
             reflection, reflectMat,
             ambient, sun, fill,
+            skyMesh: sky.mesh, skyMat: sky.mat,
             popGroup,
             seed,
             venueSpec: venueSpec || null,
@@ -305,6 +312,12 @@ export const chamber = {
             }
         }
 
+        // Song sky + matched fog. The sky replaces clear-to-black; fog takes
+        // the dome's mid colour so the horizon melts instead of banding.
+        paintSky(instance.skyMat, {
+            palette: pal, light: roomLight, style,
+            seed: instance.seed,
+        });
         // Fog via space + story: resolution (fog 0.55) closes the room in,
         // climax (0.18) opens it. Swing near AND far so the depth change reads.
         if (scene.fog) {
@@ -312,7 +325,9 @@ export const chamber = {
             const fogDepth = (space ? 12 + space.depth * 6 : 15) * (0.7 + fogMul * 0.75);
             scene.fog.near = fogDepth;
             scene.fog.far = fogDepth + 10 + fogMul * 10;
-            scene.fog.color.setRGB(c0[0] * 0.06, c0[1] * 0.06, c0[2] * 0.08);
+            const mid = instance.skyMat ? instance.skyMat.uniforms.u_mid.value : null;
+            if (mid) scene.fog.color.copy(mid);
+            else scene.fog.color.setRGB(c0[0] * 0.06, c0[1] * 0.06, c0[2] * 0.08);
         }
 
         // Rebuild population if needed (deterministic, seeded). The arrangement