Phase 2: learning engine — history, SRS review, mistakes, stats, exam, reminders

Answer history and schedules
- Every answer is recorded (deck, activity, topic, correct/wrong, time)
  in a versioned IndexedDB log (freezmo-learning v1, stores answers +
  srs), mirrored in memory for synchronous React reads and capped at
  20k answers (oldest pruned). StudyFeed records as it grades.
- Light SM-2 schedule per activity: 1 day, 3 days, then interval x
  ease; wrong answers return in ten minutes with the ease nudged down.

Review, mistakes, stats
- Library 'Smart review' card: due count, mistakes count (latest
  answer wrong — clears itself when answered correctly), today's goal
  progress. Review sessions freeze their item list at start.
- New /review (due across decks, ?mistakes=1 global or ?deck= per
  deck) built on a shared SessionFeed with the study feed's snap/keyboard
  mechanics, wake lock and a results slide.
- New /stats: day streak, five-week calendar, accuracy per subject and
  per deck, weakest topics (>=3 answers), daily-goal progress.
- Daily goal configurable in Settings (10/20/30/50).

Exam mode
- New /exam: pick decks, question count, optional timer; no hints
  (a NoHints context hides hint rows and the self-check escape);
  results with score, per-deck and per-topic breakdown; wrong answers
  land in the mistakes set through the normal history.

Reminders (conditional)
- VAPID-gated: GET/POST/DELETE /api/push and POST /api/push/test with
  the standard route pattern, RATE_LIMIT_PUSH, zod, auth before body.
  Subscriptions stored server-side as endpoint + keys only (PUSH_DIR).
  UI hidden entirely without keys; iOS install note; service worker
  push/notificationclick handlers; scripts/send-reminders.mjs for a
  cron/systemd timer; web-push added as the one server dependency.

Verified: new phase-2 suite 42/42 (history/SRS shapes from a real study
run, mistakes clearing, review session, stats math, exam timer and
breakdowns, VAPID-less hidden state plus the configured
subscribe/validate/test/delete path against a second instance) plus
regression 74/74, mobile 52/52, wizard 80/80, declutter 116/116,
animation 8/8, native 35/35, phase1 38/38, i18n 25/25. Key parity
709/709. Lint + build clean. SW freezmo-v26.

components/LibraryScreen.tsx

@@ -9,10 +9,13 @@ import { FolderBar } from "@/components/FolderBar";
 import { HomeworkCard } from "@/components/HomeworkCard";
 import { FolderIcon, UploadIcon } from "@/components/icons";
 import { SegmentedPill } from "@/components/SegmentedPill";
-import { Button, EmptyState } from "@/components/ui";
+import { Button, EmptyState, ProgressBar } from "@/components/ui";
 import { folderStore, renameFolder } from "@/lib/folders";
 import { deleteHomework, homeworkStore, sortHomework } from "@/lib/homework";
+import { learningStore } from "@/lib/history";
 import { useI18n } from "@/lib/i18n";
+import { computeStats, dueCount, mistakeCount } from "@/lib/learning";
+import { settingsStore } from "@/lib/settings";
 import { ALL_FOLDERS, folderSelection, useSelectedFolder } from "@/lib/nav";
 import { springGentle } from "@/lib/motion";
 import { UNORGANIZED_ID, type Deck } from "@/lib/schemas";
@@ -52,6 +55,26 @@ export function LibraryScreen({ initialTab = "decks" }: { initialTab?: "decks" |
   useEffect(() => {
     setNudgeDue(backupNudgeDue(decks.length));
   }, [decks.length]);
+
+  /* Learning strip: SRS due count, open mistakes, today's goal. */
+  const answers = useSyncExternalStore(
+    learningStore.subscribe,
+    learningStore.getAnswersSnapshot,
+    learningStore.getServerAnswers,
+  );
+  const srs = useSyncExternalStore(
+    learningStore.subscribe,
+    learningStore.getSrsSnapshot,
+    learningStore.getServerSrs,
+  );
+  const dailyGoal = useSyncExternalStore(
+    settingsStore.subscribe,
+    () => settingsStore.getSnapshot().dailyGoal,
+    () => 20,
+  );
+  const due = useMemo(() => dueCount(srs), [srs]);
+  const mistakes = useMemo(() => mistakeCount(answers), [answers]);
+  const todayCount = useMemo(() => computeStats(answers).todayCount, [answers]);
   const importRef = useRef<HTMLInputElement>(null);
 
   const sorted = useMemo(() => sortDecks(decks), [decks]);
@@ -233,6 +256,47 @@ export function LibraryScreen({ initialTab = "decks" }: { initialTab?: "decks" |
           exit={isPhone ? { opacity: 0, y: -6, transition: { duration: 0.16 } } : undefined}
           transition={springGentle}
         >
+      {/* learning: review due, mistakes, exam, daily goal ---------------- */}
+      <section className="card mb-5 space-y-3 p-4">
+        <div className="flex flex-wrap items-center justify-between gap-2">
+          <p className="text-[11px] font-semibold uppercase tracking-wide text-[var(--text-subtle)]">
+            {t("review.cardTitle")}
+          </p>
+          <p className="text-[11.5px] font-medium text-[var(--text-muted)]">
+            {t("library.learningToday", { n: todayCount, goal: dailyGoal })}
+          </p>
+        </div>
+        <ProgressBar value={Math.min(todayCount, dailyGoal)} max={dailyGoal} label={t("stats.today")} />
+        <div className="flex flex-wrap gap-2">
+          <Link
+            href="/review"
+            aria-disabled={due === 0}
+            className={cn(
+              "touch-target inline-flex h-10 items-center rounded-xl px-3.5 text-[13px] font-semibold transition",
+              due > 0 ? "btn-primary" : "btn-secondary pointer-events-none opacity-60",
+            )}
+          >
+            {t("review.title")} · {plural(due, "review.due")}
+          </Link>
+          <Link
+            href="/review?mistakes=1"
+            aria-disabled={mistakes === 0}
+            className={cn(
+              "touch-target inline-flex h-10 items-center rounded-xl px-3.5 text-[13px] font-semibold transition",
+              mistakes > 0 ? "btn-secondary" : "btn-secondary pointer-events-none opacity-60",
+            )}
+          >
+            {t("review.mistakesTitle")} · {plural(mistakes, "review.mistakes")}
+          </Link>
+          <Link
+            href="/exam"
+            className="btn-ghost touch-target inline-flex h-10 items-center rounded-xl px-3.5 text-[13px] font-semibold transition"
+          >
+            {t("exam.title")}
+          </Link>
+        </div>
+      </section>
+
       {/* gentle backup nudge — dismissible, never blocks ---------------- */}
       {nudgeDue ? (
         <div className="mb-5 flex flex-wrap items-center gap-3 rounded-2xl border border-[var(--hairline)] bg-[var(--surface-sunken)] px-3.5 py-3">