web: open the catalogue without a version another tab can block

docker/frontend/scripts/library-check.mjs

@@ -447,6 +447,33 @@ await page.waitForTimeout(300);
 const walked = await page.$eval('[data-key="lib-strip"]', (el) => el.scrollLeft);
 step('a wheel tick walks the strip along', shelf.sw > shelf.cw && walked > 0, `${shelf.sw}px of tiles in ${shelf.cw}px, scrolled to ${walked}`);
 
+// A catalogue another tab has open — the tab that is still running yesterday's
+// build, holding the connection the new build used to ask for a version on. The
+// screen has to come up on it: the catalogue is opened as it is, with no version
+// to reach for and nothing for the other tab to block.
+const hold = await context.newPage();
+await hold.route('**/assets/*.js', (r) => r.abort());
+await hold.goto(`${base}/library`).catch(() => {});const held = await hold.evaluate(
+  () =>
+    new Promise((resolve, reject) => {
+      const req = indexedDB.open('recipescam-library');
+      req.onsuccess = () => {
+        window.__held = req.result;
+        resolve(req.result.version);
+      };
+      req.onerror = () => reject(req.error);
+    })
+);
+await page.setViewportSize({ width: 1280, height: 720 });
+await page.goto(`${base}/library`);
+await page.waitForSelector('[data-key="lib-node-CheckRoll"]', { timeout: 30_000 });
+const seenAgain = await page.$$eval(thumbs, (els) => els.length);
+step(
+  'a catalogue another tab is holding still comes up',
+  held >= 1 && seenAgain === 3,
+  `held at version ${held}, ${seenAgain} tiles on the other tab`
+);
+
 await browser.close();
 sampleServer.close();
 app.kill('SIGTERM');