fix(plex): a collection sibling is a full Plex card, and the player's info overlay plays it

- PlexInfo's collection strip gives each card the related strip's action set: the "…" menu (with
  Restart for a touch reader), the watched toggle and the playlist add.
- `onPlayItem` is required, so no variant draws a Play that does nothing; the player's info overlay
  plays the sibling in the running player (`go(id, _, fromZero)` for its Restart).

frontend/src/components/PlexPlayer.tsx

@@ -623,6 +623,9 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
   // to that item (Back within 3 s of the next) resumes it like any other. A flag, not a consumed
   // prop: StrictMode replays this effect, and a consumed one resumed on the replay.
   const movedOnRef = useRef(false);
+  // An item `go` was asked to play from its start (a collection sibling's Restart in the info
+  // overlay); the opening item's own `fromStart` is the prop above.
+  const startAtZeroRef = useRef<string | null>(null);
   useEffect(() => {
     if (!detail || detail.id !== id || startedForRef.current === id) return;
     startedForRef.current = id;
@@ -637,7 +640,9 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
     setAudioOrd(aOrd);
     setSubOrd(subOrdForLang(detail.subtitle_streams ?? [], subLang));
     const resume =
-      detail.status !== "watched" && !(fromStart && !movedOnRef.current)
+      detail.status !== "watched" &&
+      !(fromStart && !movedOnRef.current) &&
+      startAtZeroRef.current !== id
         ? detail.position_seconds || 0
         : 0;
     void loadSession(resume);
@@ -818,8 +823,9 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
   );
 
   const go = useCallback(
-    (otherId: string | null | undefined, watchedWrite?: Promise<unknown>) => {
+    (otherId: string | null | undefined, watchedWrite?: Promise<unknown>, fromZero = false) => {
       if (otherId) {
+        startAtZeroRef.current = fromZero ? otherId : null;
         // A played-through item settles as watched, with no checkpoint at the credits (see
         // usePlexProgress's `finish`) — said BEFORE the pause below, whose own checkpoint on the
         // 'pause' event can land before the player has re-rendered for the next item. The write is
@@ -1840,7 +1846,16 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
             onClick={(e) => e.stopPropagation()}
           >
             <Suspense fallback={null}>
-              <PlexInfo detail={detail} variant="overlay" onClose={() => setInfoOpen(false)} />
+              <PlexInfo
+                detail={detail}
+                variant="overlay"
+                onClose={() => setInfoOpen(false)}
+                // A collection sibling plays right here (E28 review D1), as Next would.
+                onPlayItem={(other, fromZero) => {
+                  setInfoOpen(false);
+                  go(other, undefined, fromZero);
+                }}
+              />
             </Suspense>
           </div>
         </div>