Deep-link view settings survive file drops

Dropped files ignored pins while the URL still claimed them, so the census venue replaced the demo's pinned room. Drop loads now inherit venueSel/viz from the query, and stale bank addressing (song/seed/frame/warm) is cleared on drop while view settings stay.

flow-state/src/main.js

@@ -104,7 +104,20 @@ async function loadFile(file, { seed = null, pins = null, frame = null, warm = n
     if (state.busy) return;
     state.busy = true;
     stopPlayback();
-
+    // A dropped file carries no pins of its own — inherit the view settings
+    // from the URL (a demo deep-link's venueSel/viz), so the room and subject
+    // you came to see survive the new track. The bank path always passes an
+    // explicit pins object and is unaffected. Frame/warm never carry over:
+    // they address the old song's timeline.
+    const fromDrop = pins == null;
+    if (fromDrop) {
+        try {
+            const q = new URLSearchParams(location.search);
+            if (q.get('venueSel') || q.get('viz')) {
+                pins = { venueSel: q.get('venueSel'), viz: q.get('viz') };
+            }
+        } catch { /* non-browser — no pins */ }
+    }
     if (dom.overlay) {
         dom.overlay.hidden = true;
         dom.overlay.style.display = 'none';
@@ -136,8 +149,8 @@ async function loadFile(file, { seed = null, pins = null, frame = null, warm = n
         // Deep link from a preview (filmstrip figure, venue-gallery card):
         // pins ride into load() so the arc builds pinned layers once, then
         // the exact frame with the probe's warm-up so stateful layers land
-        // converged like the probe render. Dropped files never carry pins —
-        // only `?song=` loads pass them.
+        // converged like the probe render. Dropped files carry inherited
+        // pins (above) but always start at frame 0.
         const deepLink = !!(pins && (pins.venueSel || pins.viz)) || Number.isFinite(frame);
         // Prime before the landing seek on deep-link loads: programs link
         // asynchronously and a draw against an unlinked program is wrong
@@ -146,6 +159,7 @@ async function loadFile(file, { seed = null, pins = null, frame = null, warm = n
         if (deepLink) state.show.prime();
         seekTo(Number.isFinite(frame) ? frame : 0,
             Number.isFinite(warm) ? { warmup: warm } : {});
+        if (fromDrop) clearBankParamsFromUrl();
         renderPanel();
         document.title = `flow-state · ${state.show.fileName}`;
         console.info('[flow-state]', describeLook(state.show.look));
@@ -174,6 +188,27 @@ if (dom.changeTrack) dom.changeTrack.addEventListener('click', () => dom.fileInp
 dom.fileInput.addEventListener('change', (e) => {
     if (e.target.files[0]) loadFile(e.target.files[0]);
 });
+/**
+ * A dropped file has no URL identity, so the bank addressing it by name
+ * (?song=&seed=&frame=&warm=) must go once the file loads — otherwise the
+ * URL keeps describing the previous song while another plays (and rerolls
+ * would persist a seed against the wrong name). View settings
+ * (?venue=&venueSel=&viz=) stay: they describe how you watch, not what.
+ * Uses replaceState — no reload, no history spam.
+ */
+function clearBankParamsFromUrl() {
+    try {
+        const q = new URLSearchParams(location.search);
+        if (!q.get('song') && !q.get('seed') && !q.get('frame') && !q.get('warm')) return;
+        q.delete('song');
+        q.delete('seed');
+        q.delete('frame');
+        q.delete('warm');
+        const rest = q.toString();
+        history.replaceState(null, '', rest ? `${location.pathname}?${rest}` : location.pathname);
+    } catch { /* non-browser or sandboxed iframe */ }
+}
+
 /**
  * `?song=centre` — open a bank song straight from a debug page.
  *