fix(nav): a linked player, file and search survive what the app does by itself (review round 2)

- Playlists: a link over a playlist the account does not hold plays alone; the rail's own
  fallback no longer counts as a pick that gives the player up.
- The linked opener opens or clears nothing once the address names another player, and stops
  looking (and fetching its row) once it settled.
- Files: a list the server's cap cut — the sorted or searched one too — keeps the link, with a
  notice of its own (EN/HU).
- History: an in-place view rewrite (search refine, count, channel to channel, sub-view)
  drops a reloaded entry's overlay marks (replaceView); a landing on a channel opened from a
  search keeps the search; the Feed press on a search opens the plain feed.
- Files/Playlists: an emptied search is written at once.
- Client log: plf/cf (column text filters) are typed keys; the shell has none of its own.
- Contract: writers outside lib/ take a literal or a lib/ function's result; every URL key is
  sorted typed or not; the writer regexes are held by a fixture; sub-views named; the bookmark
  net reads page tags.
- Feed defaults in one constant; one live-search queue helper; Scheduler writes through the
  Activity codec; notRun copy (EN/HU) names Forward and a plain "Search YouTube" button.

frontend/src/modules/playlists/Playlists.tsx

@@ -586,18 +586,26 @@ function PlaylistDetail() {
   // (filtered out, gone from the list, the list emptied or out of reach) plays alone, and nothing
   // removes it from a list. In: the order seeded from it (an empty one has none to wait for), or its
   // read refused. Scoped to the playlist it was linked over: another one picked first gives it up.
+  // One the account's list does not hold (deleted since, another account's link) is out of reach
+  // as soon as that list is in: the rail then moves to another one by itself, which is no pick.
+  const [linkedOver] = useState(selectedId);
+  const linkedOutOfReach =
+    listQuery.data != null && !listQuery.data.some((p) => p.id === linkedOver);
   const linkedListIn =
+    linkedOutOfReach ||
     (detail != null && (detail.items.length === 0 || items.length > 0)) ||
-    (selectedId != null && detailQuery.isError) ||
-    (selectedId == null && listQuery.data?.length === 0);
+    (selectedId != null && detailQuery.isError);
   useOpenLinkedPlayer(
     linkedListIn,
-    (id) => shown.find((v) => v.id === id),
+    (id) => (linkedOutOfReach ? undefined : shown.find((v) => v.id === id)),
     (video, inList) => {
       if (inList) openPlayer(video.id);
-      else setPlaying({ video, queue: [video], index: 0, listId: selectedId, editable: false });
+      else {
+        const listId = linkedOutOfReach ? null : selectedId;
+        setPlaying({ video, queue: [video], index: 0, listId, editable: false });
+      }
     },
-    selectedId,
+    linkedOutOfReach ? linkedOver : selectedId,
   );
 
   async function moveItemTo(video: Video, target: Playlist) {