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/Channels.tsx

@@ -15,6 +15,9 @@ import Tooltip from "./ui/Tooltip";
 import DataTable from "./ui/DataTable";
 import Tabs, { type TabDef } from "./ui/Tabs";
 import ChannelLayoutGrid from "./ChannelLayoutGrid";
+import { ComfortPinMenu } from "./ComfortPinMenu";
+import { pinChannel } from "./comfortPin";
+import { useContextMenu } from "./ui/useContextMenu";
 import { LoadingState, StateMessage } from "./ui/QueryState";
 import { useChannelTagActions } from "../lib/useChannelTagActions";
 import { useTagSuggestions } from "./useTagSuggestions";
@@ -412,6 +415,11 @@ export default function Channels() {
     />
   );
   const hasLayout = view === "subscribed" || view === "discovery";
+  // The comfort-shelf pin on a channel row (E24 S3). ONE menu for the list, shared by the table and
+  // the card layout — they are two paints of the same rows, so a right-click must mean the same
+  // thing in both. Only mounted under the SUBSCRIBED branch below: a discovery result is not a
+  // `Channel` row yet, so pinning one could only 404.
+  const pinMenu = useContextMenu<ManagedChannel>();
   // In cards there are no column headers to sort by, so a dropdown drives the SAME shared sort state
   // the table header uses (table ↔ cards stay in sync). Table mode keeps the header clicks.
   const sortControl = (
@@ -613,6 +621,7 @@ export default function Channels() {
               onFiltersChange={setFilters}
               fixedLayout
               emptyText={t("channels.empty")}
+              rowProps={pinMenu.triggerProps}
             />
           ) : (
             <ChannelLayoutGrid
@@ -623,8 +632,14 @@ export default function Channels() {
               aboutKey="about"
               actionsKey="actions"
               emptyText={t("channels.empty")}
+              rowProps={pinMenu.triggerProps}
             />
           )}
+          <ComfortPinMenu
+            menu={pinMenu}
+            target={(c) => pinChannel(c.id)}
+            title={(c) => c.title ?? t("channels.row.thisChannel")}
+          />
         </div>
       )}
     </>