feat(e24): pin to the comfort shelf from every card and row

S3 wires the shelf's editor. The gesture is the E10 right-click menu, so the
decision "this is comfort media" can be made where the thing is — the feed, a
Plex grid, a channel row, a playlist — rather than only on the page that lists
the shelf.

One shared piece, `components/comfortPin.tsx`: the five pin-kind constructors,
the shelf query, and ONE `ActionMenuItem` that switches Pin/Unpin honestly (and
says "not known yet" with a disabled row until the shelf has answered, since a
confident "Pin" over something already pinned is exactly the quiet lie the house
rules forbid). Surfaces that already have a row menu compose the item in
(`Playlists`, `PlaylistsRail`); the rest mount `ComfortPinMenu`.

Two structural notes:

- The feed's menu lives in `VirtualFeed`, not in `Feed` — that is the list, and
  it is also what gives the channel page the gesture for free, since it renders
  `<Feed channelScoped>` all the way down.
- Cards take `menuProps` as a FUNCTION of the row, not the built props object.
  `triggerProps` is stable across renders while its return value is not, and a
  fresh object prop would blow past `VideoCard`'s memo for every card in the
  virtualized feed on every parent render.

`DataTable` and `ChannelLayoutGrid` grow a generic `rowProps` so a channel row
answers the same gesture in both of the manager's layouts; the table stays
domain-free and never learns what a menu is.

On Home the shelf tile's menu is the whole editor: four move rows (front / left
/ right / end, reusing the playlist menu's ordering idiom) plus the unpin, over
menu rows rather than drag & drop — dragging inside a horizontal, scrolling
Carousel fights the scroll, and menu rows are keyboard-reachable for free. The
reorder is optimistic on the cached payload and re-asks the server on failure
rather than showing an order that was never accepted.

The exhausted shelf tile (a pinned channel with nothing unwatched left) is
`aria-disabled`, not `disabled`: measured in Chromium, a disabled button still
receives contextmenu and pointerdown, but it loses focus — and with it Shift+F10,
the only keyboard route to the menu it most needs.

Verified end to end in the browser against the live account: all five pin kinds,
the reorder (persisted across a reload), the unpin, and the honest Unpin label on
a resume tile that is already on the shelf.

frontend/src/components/PlexCollectionView.tsx

@@ -11,6 +11,8 @@ import { showEpisodeKeys } from "../lib/plexQueue";
 import { useConfirm } from "./ConfirmProvider";
 import { BackBtn, ActionBtn, DetailHero } from "../lib/plexDetailUi";
 import { PlexPosterCard } from "./plexCards";
+import { PlexPinMenu } from "./ComfortPinMenu";
+import { useContextMenu } from "./ui/useContextMenu";
 import PlexLibraryPicker from "./PlexLibraryPicker";
 import { toggleWatchState } from "../lib/plexWatch";
 import { LoadingState, StateMessage } from "./ui/QueryState";
@@ -47,6 +49,8 @@ export default function PlexCollectionView({
   const { t } = useTranslation();
   const qc = useQueryClient();
   const confirm = useConfirm();
+  // One comfort-pin menu for the member grid (see ui/ContextMenu).
+  const pinMenu = useContextMenu<PlexCard>();
   const isAdmin = qc.getQueryData<{ role?: string }>(qk.me())?.role === "admin";
   const q = useQuery({
     queryKey: qk.plexCollections("detail", collectionId),
@@ -348,6 +352,7 @@ export default function PlexCollectionView({
                     onOpen={() => onOpenCard(c)}
                     onInfo={() => onInfoCard(c)}
                     onToggleWatched={toggleWatched}
+                    menuProps={pinMenu.triggerProps}
                   />
                   {canEdit && (
                     <button
@@ -366,6 +371,7 @@ export default function PlexCollectionView({
           )}
         </>
       )}
+      <PlexPinMenu menu={pinMenu} />
     </div>
   );
 }