fix(player): open the channel page from the player without it bouncing back

Two bugs made clicking the channel name in the video modal just close the player:
- the second PlayerModal mount (main feed path) was missing onOpenChannel, so the handler
  hit its no-op early return;
- opening the channel synchronously pushed the _chan history entry, which the player's own
  useBackToClose teardown (history.back on unmount) then immediately popped. Now the open is
  deferred to a one-shot popstate listener that fires AFTER that teardown, so the channel
  entry lands at the feed level. Verified: player → channel name → channel page; Back → feed
  (player does not reappear).

frontend/src/components/Feed.tsx

@@ -587,6 +587,7 @@ export default function Feed({
           startAt={activeVideo.startAt}
           onClose={() => setActiveVideo(null)}
           onState={onState}
+          onOpenChannel={onOpenChannel}
         />
       )}
       {isFetchingNextPage && (

frontend/src/components/PlayerModal.tsx

@@ -559,8 +559,19 @@ export default function PlayerModal({
               <div className="flex items-center gap-1.5 shrink-0 min-w-0">
                 <button
                   onClick={() => {
+                    if (!onOpenChannel) return onClose();
+                    const cid = active.channel_id;
+                    const cname = active.channel_title ?? undefined;
+                    // Closing the player pops its own history entry (useBackToClose → history.back()).
+                    // Open the channel only AFTER that pop's popstate — pushing the channel entry
+                    // before it would let the back remove it again (the bug: clicking the name only
+                    // closed the player). One-shot listener fires after App's popstate handler.
+                    const open = () => {
+                      window.removeEventListener("popstate", open);
+                      onOpenChannel(cid, cname);
+                    };
+                    window.addEventListener("popstate", open);
                     onClose();
-                    onOpenChannel?.(active.channel_id, active.channel_title ?? undefined);
                   }}
                   className="font-medium hover:text-accent truncate text-left"
                 >