feat(02-05): letter overlay + settings UI + boot save lifecycle + clock injection

- src/save/payload.ts (W2): shared buildPayloadFromStore (state, nowMs)
  + hydrateStoreFromPayload (state, payload). Two-arg signature unifies
  Settings.tsx (passes Date.now()) and PhaserGame.tsx saveSync (passes
  clock.now()). BLOCKER 3 — lastTickAt is wall-clock ms, owned by the
  application layer; the sim never writes it.
- src/ui/letter/Letter.tsx + test: D-20 full-screen overlay (UX-02);
  loads compiled letter Ink, binds plants_bloomed/fragment_titles/
  lura_was_here slots from session.pendingLetterEventBlock, dismisses
  via Tend the garden button or backdrop click. Pitfall 9 — dismiss
  calls bootstrapAudioContext synchronously inside the click handler.
- src/ui/settings/Settings.tsx + test: D-28 save-management UI
  (Export/Import/Restore). BLOCKER 2 — Import pipeline is
  importFromBase64 -> unwrap (CRC verify) -> migrate -> hydrate. No
  audio sliders, no a11y polish (Phase 8 owns those).
- src/ui/settings/persistence-toast.tsx: D-30 one-time soft toast in
  voice when navigator.storage.persist() denies. Reads
  showPersistenceToast from session slice; sets persistenceToastShown
  after the timeout fires.
- src/PhaserGame.tsx: full boot path rewrite. Clock selection
  (?devtime=fake URL flag, production-guarded by import.meta.env.PROD),
  save load (BLOCKER 1 — unwrap then migrate), silent offline catchup
  via drainTicks(silent=true), letter overlay open at >=5min absence,
  requestPersistence + showPersistenceToast wiring, Phaser start AFTER
  hydration, registerSaveLifecycleHooks with synchronous LocalStorage
  saveSync (Pitfall 7) + best-effort IDB write. W5 — lifecycle handle
  held in ref so outer cleanup detaches.
- src/store/session-slice.ts: showPersistenceToast transient flag +
  setShowPersistenceToast action.
- src/ui/journal/journal-icon.tsx: 'j' hotkey listener via
  tlg:toggle-journal CustomEvent (D-29).
- src/game/scenes/Garden.ts: formalized clock read via readClockSlot()
  helper; falls back to wallClock if window.__tlgClock missing.
- src/App.tsx: mount Letter, Settings, PersistenceToast, SettingsIcon
  (corner button); D-29 keyboard shortcuts (',' toggles Settings, 'j'
  toggles Journal via window event).
- 308/308 tests green (was 295; +13 new — 7 Letter + 6 Settings).
  npm run ci exits 0; Vite emits letter Ink as a separate lazy chunk.

src/ui/settings/persistence-toast.tsx

@@ -0,0 +1,62 @@
+import { useEffect, useState, type JSX } from 'react';
+import { useAppStore } from '../../store';
+import { uiStrings } from '../../content';
+
+/**
+ * Persistence-result toast (CONTEXT D-30 + UX-13).
+ *
+ * One-time soft toast in voice on first save if `navigator.storage.persist()`
+ * was denied; nothing if granted. State remembered via
+ * `settings.persistenceToastShown` so the toast only fires once across
+ * sessions.
+ *
+ * Triggered by src/PhaserGame.tsx after the boot path's requestPersistence
+ * call resolves with `granted=false && apiAvailable=true && !persistenceToastShown`.
+ *
+ * Anti-FOMO compliant — the copy is in the gardener-keeper voice
+ * (uiStrings[1].settings.persistence_denied_toast: "The garden may forget,
+ * if your browser asks it to."). No nag, no streak, no daily-login pressure.
+ */
+const TOAST_DURATION_MS = 6500;
+
+export function PersistenceToast({ show }: { show: boolean }): JSX.Element | null {
+  const [visible, setVisible] = useState(show);
+  const setShown = useAppStore((s) => s.setPersistenceToastShown);
+  const strings = uiStrings[1]?.settings;
+
+  useEffect(() => {
+    if (!show) {
+      setVisible(false);
+      return;
+    }
+    setVisible(true);
+    const t = setTimeout(() => {
+      setVisible(false);
+      setShown(true);
+    }, TOAST_DURATION_MS);
+    return () => clearTimeout(t);
+  }, [show, setShown]);
+
+  if (!visible || !strings) return null;
+  return (
+    <div
+      role="status"
+      data-testid="persistence-toast"
+      style={{
+        position: 'fixed',
+        bottom: 24,
+        left: 24,
+        zIndex: 30,
+        maxWidth: 420,
+        padding: '0.8rem 1.2rem',
+        background: '#1f1f23ee',
+        color: '#e8e0d0',
+        border: '1px solid #4d4d52',
+        fontFamily: 'serif',
+        fontStyle: 'italic',
+      }}
+    >
+      {strings.persistence_denied_toast}
+    </div>
+  );
+}