idle fleet slows world clock to real time instead of freezing (ISS-128)

lib/useSimClock.test.ts

@@ -1,10 +1,11 @@
 import { describe, expect, it } from 'vitest';
 import { advanceSimClock, type SimClockAnchor } from './useSimClock';
-import { WORLD_TIME_SCALE } from './worldClock';
+import { IDLE_WORLD_TIME_SCALE, WORLD_TIME_SCALE } from './worldClock';
 
 // ISS-007 (v0.16.1) — the pure extrapolation core of lib/useSimClock.ts. The hook itself is a
 // thin setInterval + re-sync wrapper covered by e2e (panes.spec.ts "ticks smoothly between polls");
-// this suite pins the math: game time advances real-time × WORLD_TIME_SCALE, frozen while idle.
+// this suite pins the math: game time advances real-time × WORLD_TIME_SCALE, and slows to
+// real-time × IDLE_WORLD_TIME_SCALE while idle (ISS-128).
 
 const anchor = (over: Partial<SimClockAnchor> = {}): SimClockAnchor => ({
   clockMs: 1_750_000_000_000,
@@ -24,10 +25,10 @@ describe('advanceSimClock', () => {
     expect(advanceSimClock(anchor(), 1_000_000)).toBe(1_750_000_000_000);
   });
 
-  it('is frozen while idle regardless of elapsed time', () => {
+  it('advances at the idle real-time rate (IDLE_WORLD_TIME_SCALE) while grounded, not frozen (ISS-128)', () => {
     const a = anchor({ advancing: false });
-    expect(advanceSimClock(a, 1_000_000)).toBe(1_750_000_000_000);
-    expect(advanceSimClock(a, 2_000_000)).toBe(1_750_000_000_000); // a full second later — still frozen
+    expect(advanceSimClock(a, 1_000_000)).toBe(1_750_000_000_000); // zero elapsed — still the anchor value
+    expect(advanceSimClock(a, 1_001_000)).toBe(1_750_000_000_000 + 1_000 * IDLE_WORLD_TIME_SCALE); // a full second later — real time, not frozen
   });
 
   it('clamps to the anchor value when nowMs is before the anchor (clock skew), never backwards', () => {