feat: v0.19.0 — ISS-011 auto-slow to 1x when all planes have landed

lib/sim/engine.ts

@@ -71,17 +71,33 @@ export async function tickOnce(inst: GameDb): Promise<schema.SimStateRow> {
   const advanceMs = sim.paused ? 0 : Math.min(elapsed, MAX_TICK_ELAPSED_MS) * sim.timeScale;
   const clockMs = Math.round(sim.clockMs + advanceMs);
 
+  let landedThisTick = 0;
   if (advanceMs > 0) {
     await expirePackages(inst, clockMs);
-    await deliverPackages(inst, clockMs);
+    // ISS-011: remember the landings so the tick can auto-slow to 1× when this was
+    // the last plane in flight.
+    landedThisTick = await deliverPackages(inst, clockMs);
     await spawnOpenPackages(inst, clockMs);
     // AFTER delivery on purpose: a plane that just landed gets work spawned
     // at its new location within the same tick.
     await spawnCoveragePackages(inst, clockMs);
   }
 
+  const sets: Partial<Pick<schema.SimStateRow, 'clockMs' | 'lastRealTickMs' | 'timeScale'>> = {
+    clockMs,
+    lastRealTickMs: nowMs,
+  };
+  // Auto-slow (ISS-011): when ≥1 plane landed this tick and NO plane remains in flight,
+  // drop the stored timeScale to 1× — persisted here so the UI slider reflects it on the
+  // next snapshot. Arrival-triggered by design: a grounded fleet at high scale is left
+  // alone (the player speeds up manually again; there is no auto-restore).
+  if (landedThisTick > 0 && !sim.paused) {
+    const flying = await inst.db.select().from(schema.planes).where(eq(schema.planes.status, 'flying'));
+    if (flying.length === 0) sets.timeScale = MIN_TIME_SCALE;
+  }
+
   // Persist lastRealTickMs even when nothing advanced — it is the tick anchor.
-  await inst.db.update(schema.simState).set({ clockMs, lastRealTickMs: nowMs });
+  await inst.db.update(schema.simState).set(sets);
   await persist(inst);
   const updated = (await inst.db.select().from(schema.simState))[0];
   if (!updated) throw new Error('sim_state row missing after tick');