Clickable previews: every still links to its exact app frame

New shared component src/ui/preview.js (appFrameUrl + previewLink): song + seed + frame + venue/venueSel deep-links. App honors ?frame= (warm seek on bank-song load) and ?venueSel= via shared pinVenueShell helper (src/venues/pin.js), which filmstrip and venue-gallery now also use. Filmstrip figures and venue-gallery cards wrap canvases; gallery cells stay unlinked (isolated scene probes, not reproducible in-app).

flow-state/src/checks/filmstrip.js

@@ -22,9 +22,9 @@
 
 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 { pinVenueShell } from '../venues/pin.js';
 import { frameDescriptor, motionDescriptor } from './variety/descriptors.js';
 import { descriptorDistance, directionOf, STRUCTURAL } from './variety/signature.js';
 import { describeStory } from '../look/Story.js';
@@ -79,13 +79,7 @@ export function renderSong(show, name, { duration, every, venueEnabled = null, v
     // 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;
-    }
+    if (sel) pinVenueShell(look, sel);
     show.useTrack(track, look);
 
     const frames = [];