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/PlaylistsRail.tsx

@@ -12,6 +12,7 @@ import { type PanelLayout } from "../lib/panelLayout";
 import FilterRail from "./FilterRail";
 import { Button } from "./ui/Button";
 import { type ActionMenuItem } from "./ui/ActionMenu";
+import { useComfortPin, pinPlaylist } from "./comfortPin";
 import { ContextMenu } from "./ui/ContextMenu";
 import { useContextMenu } from "./ui/useContextMenu";
 import { type PanelItem } from "./ui/PanelGroups";
@@ -74,6 +75,9 @@ export default function PlaylistsRail({
   const plActions = usePlaylistActions();
   // Right-click / long-press anywhere on a rail row. ONE menu for the whole list (see ui/ContextMenu).
   const railMenu = useContextMenu<Playlist>();
+  // The comfort-shelf pin composes INTO this menu rather than mounting a second one: a row can only
+  // have one right-click menu, and rename/delete/pin are all things you do to the same playlist.
+  const comfortPin = useComfortPin(railMenu.open);
   // Renaming happens IN the row that was right-clicked, not in the detail header — the point of the
   // context menu is that the action lands where the gesture did.
   const [renamingId, setRenamingId] = useState<number | null>(null);
@@ -226,6 +230,7 @@ export default function PlaylistsRail({
             setRenamingId(ctxPl.id);
           },
         },
+        ...comfortPin.item(pinPlaylist(ctxPl.id), plName(ctxPl)),
         {
           id: "delete",
           label: t("playlists.delete"),