fix(library): ring the folder a reading was asked of, from the click

docker/frontend/src/Library.tsx

@@ -1027,6 +1027,13 @@ function Catalogue() {
     [nodes, expanded]
   );
 
+  // The row a reading was asked of, spelled the way the walk spells a path (`''`
+  // for the whole roll), and whether the column holds that row at all: a reading
+  // kept to a folder whose branch the reader has folded shut has no row to wear
+  // the ring, and falls back on its roll's own row.
+  const askedFrom = live ? normPath(live.progress.from) : '';
+  const askedDrawn = askedFrom !== '' && rows.some((n) => normPath(relOf(n.key) ?? '') === askedFrom);
+
   // A remembered subfolder that no longer holds a frame falls back to the folder
   // it sits in, so the screen never opens on a node that is not drawn.
   useEffect(() => {
@@ -1659,17 +1666,19 @@ function Catalogue() {
                           const fNorm = (f.name || '').replace(/\\/g, '/');
                           return n.key === fNorm || n.key.startsWith(`${fNorm}/`) || n.key === f.name || n.key.startsWith(`${f.name}/`);
                         }) ?? folders[0] ?? null;
-                      // The row that says a reading is under way is the folder the
-                      // reading stands in — not the folder it was pointed at, which
-                      // would be the same row for the whole of an afternoon while
-                      // the work went on somewhere the reader cannot see — together
-                      // with every folder above it, so a branch folded shut still
-                      // shows the work going on under it. The roll's own row wears
-                      // it too, and for two reasons: the frames that sit in the
-                      // roll's own folder have no row but this one, and a reading
-                      // kept to one folder leaves its branch folded or its folder
-                      // off the column, which would otherwise be a whole reading
-                      // reported by the toolbar's line alone.
+                      // The row that says a reading is under way. It is first of
+                      // all the row the reading was asked of — a right click on
+                      // April is a reading of April — and it wears the ring from
+                      // the click, not from the first frame in hand: the walk
+                      // reads the catalogue and the position back before it
+                      // touches the disk, and a command that shows nothing at all
+                      // for that while is a command the reader cannot tell from
+                      // one that never ran. From there the ring follows the
+                      // reading: the folder it stands in, and every folder above
+                      // it, so a branch folded shut still shows the work going on
+                      // under it. A reading asked of the whole roll, and one whose
+                      // own row is not on the column at all, is answered by the
+                      // roll's row — the only row those frames have.
                       const isScanFolderMatch = !!(live && folder && normPath(live.folder) === normPath(folder.name));
                       const scanAt = live?.progress.at ? normPath(live.progress.at) : '';
                       // The row's own path under its own roll, spelled the way the
@@ -1682,9 +1691,12 @@ function Catalogue() {
                         n.depth === 0 || !normFolder || !n.key.startsWith(`${normFolder}/`)
                           ? ''
                           : n.key.slice(normFolder.length + 1);
+                      // The row the reading was asked of, and the roll's own row
+                      // for a reading that has no row of its own to stand on.
+                      const chosen = askedFrom === '' || !askedDrawn ? n.depth === 0 : nodeRel === askedFrom;
                       const scanning =
                         isScanFolderMatch &&
-                        (n.depth === 0 || (nodeRel !== '' && (scanAt === nodeRel || scanAt.startsWith(`${nodeRel}/`))));
+                        (chosen || (nodeRel !== '' && (scanAt === nodeRel || scanAt.startsWith(`${nodeRel}/`))));
                       // What is waiting its turn is waiting on the row it was asked
                       // of, and on every row above it: a request under a folded
                       // branch still says the roll has work queued. The roll's own