feat(player): the YouTube player and the file viewer are named in the address

The player names what it plays in its own history entry (watch, wrel, wtab): a reload or a
bookmark reopens it on the page that hosts it, with that page's list as the queue, or alone
from the catalog (GET /api/videos/{id}/row); a page that hosts none gets the shell's. Back
lands on the page's address without it (useBackToClose's url; ui/Modal passes it on). The
Files viewer and player do the same (fview, fplay). The Plex and channel-manager views are
always written in full, as their fallback is remembered state.

frontend/src/modules/playlists/Playlists.tsx

@@ -50,6 +50,7 @@ import {
 } from "../../lib/playlistsUrlState";
 import { formatRuntime } from "../../lib/format";
 import { applyView, sameOrder } from "../../lib/playlistView";
+import { useOpenLinkedPlayer } from "../../features/player/useOpenLinkedPlayer";
 const PlayerModal = lazy(() => import("../../features/player/PlayerModal"));
 import { Button } from "../../components/ui/Button";
 import { LoadingState, StateMessage } from "../../components/ui/QueryState";
@@ -580,6 +581,17 @@ function PlaylistDetail() {
     shownRef.current = shown;
     removeRef.current = removeItem;
   });
+  // A reload or a bookmark of the player reopens it once this playlist is in, its view as the queue
+  // again (the playlist and its view are in the address under it). A video the view does not show
+  // (filtered out, gone from the list) plays alone, and nothing removes it from a list.
+  useOpenLinkedPlayer(
+    detail != null && items.length > 0,
+    (id) => shown.find((v) => v.id === id),
+    (video, inList) => {
+      if (inList) openPlayer(video.id);
+      else setPlaying({ video, queue: [video], index: 0, listId: selectedId, editable: false });
+    },
+  );
 
   async function moveItemTo(video: Video, target: Playlist) {
     if (selectedId == null) return;