feat(02-01): BigQty + scheduler + sim foundations

- Install zustand@^5.0.0 + break_eternity.js@^2.1.3 as dependencies
- BigQty immutable wrapper around Decimal (D-31): factories,
  arithmetic, comparison, JSON round-trip, saturating coercion
- formatHumanReadable for K/M/B/T/scientific HUD readouts (UX-11)
- Clock interface + wallClock + FakeClock — only file in src/sim/
  allowed to read Date.now() (D-33)
- drainTicks fixed-timestep accumulator: refuses negative deltas
  (CORE-11), clamps at MAX_OFFLINE_MS=24h (CORE-03), TICK_MS=200
- computeOfflineCatchup pure descriptor for offline boundaries
- SimState root shape with BLOCKER 3 split: lastTickAt
  (wall-clock, app-layer-only) + tickCount (sim-internal monotonic)
- 52 tests across big-qty / format / clock / tick / catchup all green

src/sim/state.ts

@@ -0,0 +1,40 @@
+/**
+ * SimState — root shape of the in-memory sim world. Structurally
+ * compatible with V1Payload from src/save/migrations.ts (a SimState
+ * round-trips to a V1Payload via the application layer).
+ *
+ * Wave 0 ships placeholder unknown[] for tiles/plants — Wave 1 (Plan 02-02)
+ * fleshes them out with real interfaces in src/sim/garden/types.ts.
+ *
+ * BLOCKER 3 invariant — two distinct time fields with strict separation:
+ *   - lastTickAt: wall-clock milliseconds. Written ONLY by the application
+ *     layer at saveSync time (src/PhaserGame.tsx). The sim NEVER writes
+ *     this field. computeOfflineCatchup reads it as wall-clock ms.
+ *   - tickCount: monotonically-increasing sim-internal counter (one per
+ *     simulate() call). Used for STRY-10 narrative gating that must be
+ *     immune to wall-clock manipulation. The sim DOES write this field.
+ *     The application layer reads it but never writes it.
+ */
+export interface SimState {
+  garden: { tiles: unknown[] };
+  plants: unknown[];
+  harvestedFragmentIds: string[];
+  /** Wall-clock milliseconds at last save. Written ONLY at saveSync. */
+  lastTickAt: number;
+  /** Monotonic sim tick counter. Incremented by the sim; used for STRY-10. */
+  tickCount: number;
+  unlockedPlantTypes: string[];
+  luraBeatProgress: {
+    arrived: boolean;
+    mid: boolean;
+    farewell: boolean;
+    pending: 'arrival' | 'mid' | 'farewell' | null;
+  };
+  offlineEvents: unknown | null;
+  settings: {
+    musicVolume: number;
+    ambientVolume: number;
+    sfxVolume: number;
+    persistenceToastShown: boolean;
+  };
+}