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/filmstrip.html

@@ -88,6 +88,7 @@
     <div class="bar" id="bar">
         <span class="spinner"></span>
         <button id="rebuild">rebuild</button>
+        <select id="venueSel" title="pin one venue in every row, or census"></select>
         <select id="sort">
             <option value="direction">sort: least direction first</option>
             <option value="drift">sort: least drift first</option>
@@ -103,6 +104,7 @@
 
 <script type="module">
 import { buildFilmstrip, songNames, STRIP, DEFAULT_EVERY, DEFAULT_DURATION } from '/src/checks/filmstrip.js';
+import { venues } from '/src/venues/registry.js';
 import { blit } from '/src/checks/blit.js';
 import { hashString } from '/src/engine/rng.js';
 import {
@@ -115,6 +117,7 @@ const every = Number(params.get('every')) || DEFAULT_EVERY;
 const duration = Number(params.get('duration')) || DEFAULT_DURATION;
 const only = params.get('song') ? params.get('song').split(',') : null;
 const venueEnabled = params.get('venue') === '1';
+const venueSelParam = params.get('venueSel') || '';
 
 document.getElementById('everyLabel').textContent = every;
 
@@ -122,9 +125,21 @@ const bar = document.getElementById('bar');
 const out = document.getElementById('out');
 const status = document.getElementById('status');
 const sortSel = document.getElementById('sort');
+const venueSel = document.getElementById('venueSel');
 const progress = document.querySelector('#progress i');
 const rebuildBtn = document.getElementById('rebuild');
 
+venueSel.innerHTML = `<option value="">all venues (census)</option>` +
+    venues.map((v) => `<option value="${v.name}">${v.name} (${v.archetype})</option>`).join('');
+if ([...venueSel.options].some((o) => o.value === venueSelParam)) venueSel.value = venueSelParam;
+venueSel.addEventListener('change', () => {
+    const p = new URLSearchParams(location.search);
+    if (venueSel.value) p.set('venueSel', venueSel.value);
+    else p.delete('venueSel');
+    history.replaceState(null, '', `${location.pathname}?${p}`);
+    build();
+});
+
 let rows = [];
 
 // Read against the arcless reference the variety report prints: around zero is
@@ -224,7 +239,8 @@ function summarise(built) {
         ? rows.reduce((a, r) => a + (r.direction || 0), 0) / rows.length : 0;
     const meanAgit = rows.length
         ? rows.reduce((a, r) => a + (r.agitation ?? 0), 0) / rows.length : 0;
-    return `${rows.length} songs · every ${every}s of ${duration}s · ` +
+    const venueNote = venueSel.value ? ` · venue ${venueSel.value}` : (venueEnabled ? ' · venues from census' : '');
+    return `${rows.length} songs · every ${every}s of ${duration}s${venueNote} · ` +
         `mean direction ${meanDir.toFixed(2)} · ${flat} with no direction` +
         ` · mean agit ${meanAgit.toFixed(2)} · ${agited} agitated (≥${AGIT_CEILING.toFixed(2)})${validatedNote}` +
         (built ? ` · built ${new Date(built).toLocaleString()}` : '');
@@ -232,7 +248,7 @@ function summarise(built) {
 
 // The cache key carries the sampling parameters as well as the source, so
 // changing `?every=` does not silently show you the previous spacing's pixels.
-const cacheKey = () => `filmstrip:${every}:${duration}:${only ? only.join(',') : 'all'}:v${venueEnabled ? 1 : 0}:${sourceFingerprint()}`;
+const cacheKey = () => `filmstrip:${every}:${duration}:${only ? only.join(',') : 'all'}:v${venueEnabled ? 1 : 0}:${venueSel.value || 'auto'}:${sourceFingerprint()}`;
 
 async function build() {
     bar.classList.add('building');
@@ -242,7 +258,7 @@ async function build() {
 
     const total = (only || songNames()).length;
     const built = await buildFilmstrip({
-        duration, every, names: only, venueEnabled,
+        duration, every, names: only, venueEnabled, venueSel: venueSel.value || null,
         // Painted as they land, in bank order, rather than after the whole run.
         // A full build is a couple of minutes of GPU work and the interesting
         // failure — a strip whose frames could be shuffled — is visible in the