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/lib/api/feed.ts

@@ -314,6 +314,9 @@ export const feedApi = {
       duration_seconds: Math.floor(durationSeconds),
     }),
   videoDetail: (id: string): Promise<VideoDetail> => req(`/api/videos/${id}`),
+  /** One catalog video as the feed lists it (this user's state with it): what a player opened from an
+   *  address starts from. */
+  videoRow: (id: string): Promise<Video> => req(`/api/videos/${encodeURIComponent(id)}/row`),
   // One file of a Google Takeout export, its bytes as they are; the server tells the two apart.
   takeoutUpload: (file: File): Promise<TakeoutUpload> => uploadReq("/api/takeout", file),
   takeoutStatus: (): Promise<TakeoutStatus> => req("/api/takeout"),