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/checks/filmstrip.js

@@ -22,6 +22,7 @@
 
 import { Show, FADE_SECONDS } from '../Show.js';
 import { generateLook } from '../look/LookGenerator.js';
+import { venues } from '../venues/registry.js';
 import { song, SONGS } from '../audio/songbank.js';
 import { hashString } from '../engine/rng.js';
 import { frameDescriptor, motionDescriptor } from './variety/descriptors.js';
@@ -69,12 +70,22 @@ function blockMean(byBlock) {
  *
  * @returns {{name, frames: Array, drift: number, direction: number, look}}
  */
-export function renderSong(show, name, { duration, every, venueEnabled = null }) {
+export function renderSong(show, name, { duration, every, venueEnabled = null, venueSel = null }) {
     const { track } = song(name, { duration });
     // Seeded off the song's name, so a strip is stable between rebuilds and two
     // songs are not accidentally handed the same look.
     const venueFlag = venueEnabled !== null ? !!venueEnabled : (typeof location !== 'undefined' && new URLSearchParams(location.search).get('venue') === '1');
     const look = generateLook(track, { seed: hashString(name), venueEnabled: venueFlag });
+    // Pin one venue in every row (same shell-swap as the venue gallery): the
+    // VenueSpec population stays the census one, only the shell is forced.
+    const sel = venueSel || (typeof location !== 'undefined' && new URLSearchParams(location.search).get('venueSel')) || null;
+    if (sel && look.venue) {
+        const picked = venues.find((v) => v.name === sel);
+        if (!picked) throw new Error(`unknown venue "${sel}"`);
+        look.venue.module = picked;
+        look.venue.name = picked.name;
+        look.venue.archetype = picked.archetype;
+    }
     show.useTrack(track, look);
 
     const frames = [];
@@ -208,6 +219,7 @@ function momentAt(story, index) {
  */
 export async function buildFilmstrip({
     duration = DEFAULT_DURATION, every = DEFAULT_EVERY, names = null, venueEnabled = null,
+    venueSel = null,
     onSong = null, onSongStart = null,
 } = {}) {
     const list = names && names.length ? names : songNames();
@@ -225,7 +237,7 @@ export async function buildFilmstrip({
             }
             let row;
             try {
-                row = renderSong(show, list[i], { duration, every, venueEnabled });
+                row = renderSong(show, list[i], { duration, every, venueEnabled, venueSel });
             } catch (err) {
                 row = { name: list[i], frames: [], shots: [], drift: 0, direction: 0, error: err.message };
             }