Fixed world clock: no player time controls (ISS-117)

The world always runs at WORLD_TIME_SCALE = 24 (lib/worldClock.ts). A server
background tick (instrumentation.ts -> startBackgroundTick, 1 s interval)
advances the sim with no open browser; idle-pause freezes the clock exactly
while no plane is flying or in repair. Fresh worlds start year 2000
(STARTING_CLOCK_MS in seed.ts).

- Removed: POST /api/sim + OpenAPI entry, applyTimeControls/clampTimeScale,
  lib/timeScale.ts, LeftPane pause button + scale slider machinery,
  ISS-057 slow-on-landing/resume in flyPlane.
- Snapshot simState is now { clockMs } only; client extrapolates at the fixed
  rate between polls and freezes while idle (useSimClock).
- New test-only hook POST /api/test/set-timescale behind FLIGHT_TEST_HOOKS=1
  (sibling of set-health); all e2e setScale helpers call it, afterEach restores
  the world rate. E2E pause tests replaced by idle-pause assertions; sim.spec.ts
  activates the world via set-health + /repair for advance/expiry tests.

lib/useSimClock.test.ts

@@ -1,49 +1,45 @@
 import { describe, expect, it } from 'vitest';
 import { advanceSimClock, type SimClockAnchor } from './useSimClock';
+import { 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 × timeScale, frozen while paused.
+// this suite pins the math: game time advances real-time × WORLD_TIME_SCALE, frozen while idle.
 
 const anchor = (over: Partial<SimClockAnchor> = {}): SimClockAnchor => ({
   clockMs: 1_750_000_000_000,
   at: 1_000_000,
-  timeScale: 1,
-  paused: false,
+  advancing: true,
   ...over,
 });
 
 describe('advanceSimClock', () => {
-  it('advances by exactly elapsed real-time × timeScale while running', () => {
-    expect(advanceSimClock(anchor(), 1_001_000)).toBe(1_750_000_000_000 + 1_000); // scale 1: 1 s real = 1 s game
-    expect(advanceSimClock(anchor({ timeScale: 25 }), 1_002_500)).toBe(1_750_000_000_000 + 62_500);
-    // The e2e scenario: scale 1000, 2.5 s real → 2 500 game seconds.
-    expect(advanceSimClock(anchor({ timeScale: 1000 }), 1_002_500)).toBe(1_750_000_000_000 + 2_500_000);
+  it('advances by exactly elapsed real-time × WORLD_TIME_SCALE while running', () => {
+    expect(advanceSimClock(anchor(), 1_001_000)).toBe(1_750_000_000_000 + 1_000 * WORLD_TIME_SCALE);
+    // The e2e scenario: ~2.6 s real at the fixed world rate.
+    expect(advanceSimClock(anchor(), 1_002_600)).toBe(1_750_000_000_000 + 2_600 * WORLD_TIME_SCALE);
   });
 
   it('returns the anchor value exactly at zero elapsed', () => {
-    expect(advanceSimClock(anchor({ timeScale: 1000 }), 1_000_000)).toBe(1_750_000_000_000);
+    expect(advanceSimClock(anchor(), 1_000_000)).toBe(1_750_000_000_000);
   });
 
-  it('is frozen while paused regardless of elapsed or scale', () => {
-    const a = anchor({ timeScale: 1000, paused: true });
+  it('is frozen while idle regardless of elapsed time', () => {
+    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
   });
 
   it('clamps to the anchor value when nowMs is before the anchor (clock skew), never backwards', () => {
-    expect(advanceSimClock(anchor({ timeScale: 1000 }), 999_999)).toBe(1_750_000_000_000);
-    expect(advanceSimClock(anchor({ paused: true }), 999_999)).toBe(1_750_000_000_000);
+    expect(advanceSimClock(anchor(), 999_999)).toBe(1_750_000_000_000);
+    expect(advanceSimClock(anchor({ advancing: false }), 999_999)).toBe(1_750_000_000_000);
   });
 
-  it('mirrors the server tick model (tickOnce): advance = elapsed × timeScale while actively polled', () => {
+  it('mirrors the server tick model (tickOnce): advance = elapsed × WORLD_TIME_SCALE while actively polled', () => {
     // lib/sim/engine.ts: clockMs += min(now − lastRealTickMs, MAX_TICK_ELAPSED_MS) × timeScale.
     // For gaps under the 2 s clamp the client extrapolation is exactly the server's own formula.
-    const scale = 50;
     for (const gap of [1, 250, 999, 1_999]) {
-      expect(advanceSimClock(anchor({ timeScale: scale }), 1_000_000 + gap)).toBe(
-        1_750_000_000_000 + gap * scale,
-      );
+      expect(advanceSimClock(anchor(), 1_000_000 + gap)).toBe(1_750_000_000_000 + gap * WORLD_TIME_SCALE);
     }
   });
 });