web: fold a folder's rows without folding its frames

docker/frontend/scripts/library-check.mjs

@@ -229,6 +229,28 @@ step(
   JSON.stringify(nodes)
 );
 
+// A row with children folds its subtree on the same click that opens it, and the
+// frames it holds stay in the strip — the tree narrows, the pictures do not.
+await page.click('[data-key="lib-node-CheckRoll"]');
+await page.waitForFunction(() => document.querySelectorAll('[data-key^="lib-node-"]').length === 1, null, {
+  timeout: 10_000,
+  polling: 50,
+});
+const foldedThumbs = await page.$$eval(thumbs, (els) => els.length);
+const foldedMeta = await page.locator('[data-key="lib-stage-meta"]').innerText();
+const shut = await page.getAttribute('[data-key="lib-node-CheckRoll"]', 'aria-expanded');
+step(
+  'a folder folds its subtree and keeps its frames in the strip',
+  foldedThumbs === 3 && shut === 'false' && /P1010256/.test(foldedMeta),
+  `${foldedThumbs} tiles, aria-expanded=${shut}, stage ${foldedMeta.split('\n')[0]}`
+);
+await page.click('[data-key="lib-node-CheckRoll"]');
+await page.waitForFunction(() => document.querySelectorAll('[data-key^="lib-node-"]').length === 3, null, {
+  timeout: 10_000,
+  polling: 50,
+});
+step('the same click draws it open again', true, '3 rows');
+
 // Opening the subfolder redraws the strip and the frame above it.
 await page.click('[data-key="lib-node-CheckRoll/2026"]');
 await page.waitForFunction((sel) => document.querySelectorAll(sel).length === 2, thumbs, { timeout: 30_000 });