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/Playlists.tsx

@@ -50,6 +50,7 @@ import { applyView, sameOrder } from "../lib/playlistView";
 const PlayerModal = lazy(() => import("./PlayerModal"));
 import { Button } from "./ui/Button";
 import { type ActionMenuItem } from "./ui/ActionMenu";
+import { useComfortPin, pinVideo } from "./comfortPin";
 import { ContextMenu } from "./ui/ContextMenu";
 import { useContextMenu } from "./ui/useContextMenu";
 import UndoToolbar from "./ui/UndoToolbar";
@@ -220,6 +221,9 @@ export default function Playlists() {
   // ONE context menu for the whole table, not one popover per <tr> (see ui/ContextMenu): the row it
   // belongs to is `rowMenu.target`, and the panel anchors to the pointer.
   const rowMenu = useContextMenu<Video>();
+  // The comfort-shelf pin composes into the row's existing menu (E24 S3) rather than mounting a
+  // second one on the same <tr>.
+  const comfortPin = useComfortPin(rowMenu.open);
 
   const listQuery = useQuery({
     queryKey: qk.playlists(),
@@ -613,6 +617,7 @@ export default function Playlists() {
           icon: <Play className="w-4 h-4" />,
           onSelect: () => setPlayingId(ctxRow.id),
         },
+        ...comfortPin.item(pinVideo(ctxRow.id), ctxRow.title ?? ""),
         ...(canEdit
           ? ([
               moveTargets.length