Report question: skip a broken card and tell the server

A generated matching card arrived on a phone with three identical
definitions (the generation guards now drop those), but there was no way
to get past a bad card from inside a session. The feed chrome (deck
study, review, mistakes and exam) now has the red "!" control: one tap
records the question, skips to the next card and shows an Undo toast.

- lib/question-reports.ts: the local list (freezmo.reports.v1, zod on
  read, capped 200) is the skip state — reported cards leave every
  session type, count as "not attempted" in the results instead of
  wrong, and Undo takes a report back. A deck where everything is
  reported stays studiable so it can be regenerated.
- POST /api/reports appends one JSON line per report to
  REPORTS_DIR/reports.jsonl (shared/freezmo/reports in production, the
  dev data dir in dev). Deliberately write-only: the question text is
  readable on the server (that is the point — prompt tuning) but never
  over HTTP, since the app has no auth. Best effort: offline reports stay
  local.
- The button: a red outlined rounded square with "!", the chrome's
  control size, in both feed headers (hidden on the results slide).
- config: REPORTS_DIR + RATE_LIMIT_REPORTS (20); the deploy creates the
  shared reports dir; the dev unit and AGENTS.md note the new server
  data location.
- Suites: phase-1 (append + validation + no GET), phase-2 (button, toast,
  server POST, local copy, skip counter, hidden next session, Undo, exam
  pool). SW -> freezmo-v38.

components/StudyFeed.tsx

@@ -11,11 +11,13 @@ import { materialiseActivities } from "@/lib/deck-ops";
 import { haptic } from "@/lib/haptics";
 import { recordAnswer } from "@/lib/history";
 import { useI18n } from "@/lib/i18n";
+import { withoutReported } from "@/lib/question-reports";
 import type { Activity, Deck } from "@/lib/schemas";
 import { recordAttempt, upsertDeck } from "@/lib/storage";
 import { useWakeLock } from "@/lib/use-wake-lock";
 import { cn } from "@/lib/utils";
 import { BoltIcon, FlameIcon, XIcon } from "@/components/icons";
+import { ReportQuestionButton } from "@/components/ReportQuestionButton";
 import { Button, ProgressBar } from "@/components/ui";
 
 import { ResultsScreen } from "./ResultsScreen";
@@ -27,7 +29,11 @@ export function StudyFeed({ deck }: { deck: Deck }) {
   /* Keep the screen awake for the whole study session (feature-detected). */
   useWakeLock(true);
   const [currentDeck, setCurrentDeck] = useState(deck);
-  const [queue, setQueue] = useState<Activity[]>(deck.activities);
+  // Reported questions never enter a session; a fully reported deck stays
+  // studiable (withoutReported falls back to the full list).
+  const [queue, setQueue] = useState<Activity[]>(() => withoutReported(deck.id, deck.activities));
+  /** Ids reported during this run: skipped, so they are not "missed". */
+  const [skipped, setSkipped] = useState<string[]>([]);
   const [index, setIndex] = useState(0);
   const [results, setResults] = useState<Record<string, AttemptResult>>({});
   const [xp, setXp] = useState(0);
@@ -107,7 +113,8 @@ export function StudyFeed({ deck }: { deck: Deck }) {
       recordedRef.current = true;
       const answered = Object.values(results);
       const correct = answered.filter((entry) => entry.correct).length;
-      const score = total > 0 ? (correct / total) * 100 : 0;
+      const attempted = Math.max(0, total - skipped.length);
+      const score = attempted > 0 ? (correct / attempted) * 100 : 0;
       // Only a run with at least one answer counts. Without this, the scroll
       // anchoring shift when a regenerated deck swaps in could fire a bogus
       // 0% attempt before the feed had snapped back to the first slide.
@@ -117,7 +124,7 @@ export function StudyFeed({ deck }: { deck: Deck }) {
         void celebrate("big");
       }
     }
-  }, [finished, results, total, currentDeck.id, retryMode]);
+  }, [finished, results, total, skipped.length, currentDeck.id, retryMode]);
 
   const handleAnswered = useCallback(
     (activity: Activity, correct: boolean, meta?: { userAnswer?: string }) => {
@@ -150,10 +157,13 @@ export function StudyFeed({ deck }: { deck: Deck }) {
   );
 
   const missed = useMemo(
-    () => queue.filter((activity) => !results[activity.id]?.correct),
-    [queue, results],
+    () => queue.filter((activity) => !skipped.includes(activity.id) && !results[activity.id]?.correct),
+    [queue, results, skipped],
   );
 
+  /** What the results screen counts: reported cards were never attempted. */
+  const attemptedTotal = Math.max(0, total - skipped.length);
+
   const correctCount = useMemo(
     () => queue.filter((activity) => results[activity.id]?.correct).length,
     [queue, results],
@@ -163,6 +173,7 @@ export function StudyFeed({ deck }: { deck: Deck }) {
     (activities: Activity[], retry: boolean) => {
       setQueue(activities);
       setResults({});
+      setSkipped([]);
       setStreak(0);
       setRetryMode(retry);
       recordedRef.current = retry; // don't overwrite the best score with a retry run
@@ -267,6 +278,16 @@ export function StudyFeed({ deck }: { deck: Deck }) {
                 <BoltIcon className="size-3.5" />
                 {xp}
               </span>
+              {!finished && queue[index] ? (
+                <ReportQuestionButton
+                  deck={currentDeck}
+                  activity={queue[index]}
+                  onSkip={() => {
+                    setSkipped((current) => [...current, queue[index].id]);
+                    goTo(index + 1);
+                  }}
+                />
+              ) : null}
             </div>
           </div>
           <div className="flex items-center justify-between gap-2 text-[11px] font-semibold text-[var(--text-muted)]">
@@ -318,13 +339,13 @@ export function StudyFeed({ deck }: { deck: Deck }) {
               deck={currentDeck}
               xp={xp}
               bestStreak={bestStreak}
-              total={total}
+              total={attemptedTotal}
               correct={correctCount}
               missed={missed}
               results={results}
               retryMode={retryMode}
               onRetryMissed={() => restart(missed, true)}
-              onRestart={() => restart(currentDeck.activities, false)}
+              onRestart={() => restart(withoutReported(currentDeck.id, currentDeck.activities), false)}
               onRegenerate={regenerate}
               regenerating={regenerating}
               regenerateError={regenerateError}