perf(feed): stop the card-action + player-close feed refetch storm (E2 S5, PERF-2)

Marking a card watched/hidden/reset and closing the player each fired a full
`invalidateQueries(qk.feed())`, refetching EVERY loaded infinite-query page — 10
pages x a few quick marks = ~50 feed refetches, each a full scan (x PERF-1). The
optimistic `overrides` layer + the matchesView filter already render the correct
state (a hidden/watched card drops out instantly), so the refetch was pure waste.

Switch these paths to `refetchType: "none"`: the queries are marked stale but not
refetched now; the next filter change / remount pulls fresh server data. Applies
to the two Feed card-action paths (setState/clearState) and the PlayerModal
close (feed + playlists — progress is already persisted server-side, only the
on-screen resume bar waits for the next natural refetch).

Left as immediate refetch on purpose: channel/tag/playlist mutations (one-off, on
pages where the main feed is unmounted anyway) and the onboarding / notification-
undo paths (which must reveal the changed content right away). Gate green:
frontend tsc/eslint/knip/prettier/222 vitest (backend unchanged, 344 pytest).

frontend/src/components/Feed.tsx

@@ -254,7 +254,11 @@ export default function Feed({
       api
         .setState(id, status)
         .then(() => {
-          qc.invalidateQueries({ queryKey: qk.feed() });
+          // Mark stale WITHOUT refetching: the optimistic `overrides` layer + the matchesView filter
+          // already show the correct state (a hidden/watched card drops out immediately), so refetching
+          // every loaded infinite-query page here was pure waste — 10 pages x rapid marks = a refetch
+          // storm (PERF-2). The next filter change / remount refetches fresh from the server.
+          qc.invalidateQueries({ queryKey: qk.feed(), refetchType: "none" });
           if (status === "hidden") {
             const v = loadedRef.current.find((x) => x.id === id);
             notify({
@@ -311,7 +315,8 @@ export default function Feed({
       setOverrides((o) => ({ ...o, [id]: "new" }));
       api
         .clearState(id)
-        .then(() => qc.invalidateQueries({ queryKey: qk.feed() }))
+        // Stale-mark only (see setState above): the optimistic override already reset the card.
+        .then(() => qc.invalidateQueries({ queryKey: qk.feed(), refetchType: "none" }))
         .catch(() =>
           setOverrides((o) => {
             const next = { ...o };

frontend/src/components/PlayerModal.tsx

@@ -862,10 +862,13 @@ export default function PlayerModal({
       cancelled = true;
       window.clearInterval(timer);
       window.removeEventListener("pagehide", onHide);
-      // Final flush, then refresh the feed + playlists so resume bars reflect this session.
+      // Final flush, then mark the feed + playlists stale so resume bars reflect this session on the
+      // next natural refetch — WITHOUT refetching every loaded feed page on each player close (PERF-2:
+      // opening/closing the player through a watch session otherwise re-runs the whole infinite query
+      // each time). Progress is already persisted server-side; only the on-screen resume bar waits.
       Promise.resolve(persist()).finally(() => {
-        qc.invalidateQueries({ queryKey: qk.feed() });
-        qc.invalidateQueries({ queryKey: qk.playlist() });
+        qc.invalidateQueries({ queryKey: qk.feed(), refetchType: "none" });
+        qc.invalidateQueries({ queryKey: qk.playlist(), refetchType: "none" });
       });
       const p = playerRef.current;
       if (p && typeof p.destroy === "function") {