fix(player): related marks survive, Restart restarts, and refused pages offer nothing to click

- Every state and Watch-later write goes through features/video/videoWrites,
  which marks the never-refetched lists (related lists, live searches) once
  the server has it; a contract test holds it. The Notification Center's
  undo, the feed's reset and the Watch-later toggles skipped it before.
- Confirmed marks are also kept apart (qk.videoMarks) and laid over the
  related rows: a Show more page landing later rebuilt them from the pages
  it read when it started, and dropped a mark made meanwhile.
- Restart on a related video starts at 0 (the session's stored position
  won before), and on the one already playing it seeks.
- The watched toggle remembers each video's mark: Back showed the opened
  video's launch-time state after a related one was marked.
- The help sheet leaves out the player's keys while a layer above it has
  them waiting.
- After a refusal a retry cannot answer, neither Show more (related) nor
  Load more (live search) is offered; a failed live-search page keeps the
  results already read and says why under them.
- The related cap message counts requests, as the cap does.

frontend/src/modules/feed/Feed.tsx

@@ -22,14 +22,26 @@ import {
   type LucideIcon,
 } from "lucide-react";
 import { YouTubeIcon } from "../../lib/brandIcons";
-import { api, HttpError, type FeedFilters, type Video, type VideoStatus } from "../../lib/api";
+import {
+  api,
+  HttpError,
+  refusalReason,
+  type FeedFilters,
+  type Video,
+  type VideoStatus,
+} from "../../lib/api";
 import i18n from "../../i18n";
 import { notifyActionError } from "../../lib/actionErrors";
 import { announceVideoState, type NoticeVideo } from "../../features/video/stateNotice";
+import {
+  resetVideoState,
+  writeVideoState,
+  writeWatchLater,
+} from "../../features/video/videoWrites";
 import { notify } from "../../lib/notifications";
 import { useMe } from "../../lib/useMe";
 import { useDebounced } from "../../lib/useDebounced";
-import { patchCachedProgress, patchRelated, progressFlushes } from "../../lib/progressCache";
+import { patchCachedProgress, progressFlushes } from "../../lib/progressCache";
 import {
   buildSort,
   feedSortOptions,
@@ -124,6 +136,15 @@ const withoutWrite = <T,>(o: Overrides<T>, id: string, seq: number): Overrides<T
 // How many live-search results one fetch asks for; `Load more` pulls another batch of the same size.
 const YT_COUNTS = [20, 40, 60, 100] as const;
 
+// The live-search refusals a retry cannot answer: the day's cap, turned off on this instance, the
+// shared budget spent (ours, or YouTube's own) — tomorrow or the admin does.
+const SEARCH_FINAL_REASONS = new Set([
+  "search_daily_limit",
+  "search_disabled",
+  "quota_spent",
+  "quota",
+]);
+
 export default function Feed({
   filters,
   setFilters,
@@ -358,7 +379,7 @@ export default function Feed({
     (id: string, status: VideoStatus, video?: NoticeVideo) => {
       const seq = ++writeSeq.current;
       setOverrides((o) => ({ ...o, [id]: { value: status, seq } }));
-      const write = api.setState(id, status);
+      const write = writeVideoState(qc, id, status);
       trackSessionWrite(write);
       // Refetch once the server has the change so other views (e.g. Hidden) are in sync.
       // Announce the change only AFTER the server confirms it: a "Marked watched"/"Hidden"
@@ -373,7 +394,6 @@ export default function Feed({
           // storm (PERF-2). The next filter change / remount refetches fresh from the server.
           answered.current.add(seq);
           qc.invalidateQueries({ queryKey: qk.feed(), refetchType: "none" });
-          patchRelated(qc, id, { status });
           // The video the player is on may be none of this list's (a related one): it names itself.
           const v = video ?? loadedRef.current.find((x) => x.id === id);
           announceVideoState(id, status, v, () => onStateRef.current(id, "new"));
@@ -401,8 +421,7 @@ export default function Feed({
       const before = loadedRef.current.find((v) => v.id === id)?.position_seconds;
       patchCachedProgress(qc, new Map([[id, 0]]));
       resets.current.set(id, seq);
-      api
-        .clearState(id)
+      resetVideoState(qc, id)
         // Stale-mark only (see setState above): the optimistic override already reset the card.
         .then(() => {
           answered.current.add(seq);
@@ -423,7 +442,7 @@ export default function Feed({
     (id: string, saved: boolean) => {
       const seq = ++writeSeq.current;
       setSavedOverrides((o) => ({ ...o, [id]: { value: saved, seq } }));
-      (saved ? api.watchLaterAdd(id) : api.watchLaterRemove(id))
+      writeWatchLater(qc, id, saved)
         .then(() => {
           answered.current.add(seq);
           qc.invalidateQueries({ queryKey: qk.playlists() });
@@ -491,6 +510,9 @@ export default function Feed({
         : ytQuery.isError
           ? t("feed.yt.error")
           : null;
+    // A refusal a retry cannot answer (the day's cap, turned off, the shared budget): Load more —
+    // the same request — is not offered after it.
+    const ytFinal = SEARCH_FINAL_REASONS.has(refusalReason(ytQuery.error) ?? "");
     // The backend reports which source served the search; scrape spends no search quota, so we
     // drop the quota warning + "uses quota" wording in that mode.
     const zeroQuota = ytQuery.data?.pages?.[0]?.source === "scrape";
@@ -577,7 +599,7 @@ export default function Feed({
 
         {ytQuery.isLoading ? (
           <div className="py-16 text-center text-muted">{t("feed.yt.searching")}</div>
-        ) : ytError ? (
+        ) : ytError && !ytItems.length ? (
           <div className="py-16 text-center text-muted max-w-md mx-auto">{ytError}</div>
         ) : ytItems.length === 0 ? (
           <div className="py-16 text-center text-muted">{t("feed.yt.noResults")}</div>
@@ -594,7 +616,7 @@ export default function Feed({
               isFetching={false}
               fetchNextPage={() => {}}
             />
-            {ytQuery.hasNextPage && (
+            {ytQuery.hasNextPage && !ytFinal && (
               <div className="text-center pt-4">
                 <Button
                   variant="outline"
@@ -611,6 +633,13 @@ export default function Feed({
                 </Button>
               </div>
             )}
+            {/* A page that failed after others loaded: they stay, and the failure is said under
+                them (Load more above is the retry, when there is one). */}
+            {ytError && (
+              <StateMessage tone="error" compact className="mt-3">
+                {ytError}
+              </StateMessage>
+            )}
           </>
         )}