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/openapi.test.ts

@@ -3,7 +3,7 @@ import { describe, expect, it } from 'vitest';
 import { openApiSpec } from './openapi';
 
 describe('OpenAPI spec', () => {
-  it('documents exactly the thirteen public endpoints (4 read + 9 player actions)', () => {
+  it('documents exactly the twelve public endpoints (3 read + 9 player actions)', () => {
     expect(Object.keys(openApiSpec.paths).sort()).toEqual([
       '/api/airports',
       '/api/market/buy-plane',
@@ -15,7 +15,6 @@ describe('OpenAPI spec', () => {
       '/api/planes/{planeId}/queue', // v0.25.0 (ISS-043)
       '/api/planes/{planeId}/queue/cancel', // v0.25.0 (ISS-043)
       '/api/planes/{planeId}/repair', // v0.39.0 (ISS-069)
-      '/api/sim',
       '/api/state',
       '/api/version',
     ]);
@@ -147,36 +146,14 @@ describe('OpenAPI spec', () => {
       'weightKg', // v0.27.0 (ISS-045) — package weight in kg
     ]);
 
+    // ISS-117 (v0.52.0): the snapshot carries only the game clock — time controls are gone.
     const sim = openApiSpec.components.schemas.SimState.properties;
-    expect(Object.keys(sim).sort()).toEqual(['clockMs', 'paused', 'timeScale']);
+    expect(Object.keys(sim).sort()).toEqual(['clockMs']);
 
     const packageStatus = openApiSpec.components.schemas.PackageState.properties.status;
     expect(packageStatus.enum.sort()).toEqual(['abandoned', 'delivered', 'expired', 'ignored', 'loaded', 'open']); // v0.29.0 (ISS-047 part B)
   });
 
-  it('describes POST /api/sim as SimControlsRequest → SimState with a 400 error shape', () => {
-    const post = openApiSpec.paths['/api/sim'].post;
-    expect(post.operationId).toBe('setSimControls');
-
-    const requestSchema = post.requestBody.content['application/json'].schema;
-    expect(requestSchema.$ref).toBe('#/components/schemas/SimControlsRequest');
-
-    const ok = post.responses[200].content['application/json'].schema;
-    expect(ok.$ref).toBe('#/components/schemas/SimState');
-    const bad = post.responses[400].content['application/json'].schema;
-    expect(bad.$ref).toBe('#/components/schemas/Error');
-
-    const controls = openApiSpec.components.schemas.SimControlsRequest.properties;
-    expect(Object.keys(controls).sort()).toEqual(['paused', 'timeScale']);
-    expect(controls.timeScale.type).toBe('number');
-    expect(controls.timeScale.minimum).toBe(1);
-    expect(controls.timeScale.maximum).toBe(1000);
-    expect(controls.paused.type).toBe('boolean');
-
-    const error = openApiSpec.components.schemas.Error.properties;
-    expect(Object.keys(error)).toEqual(['error']);
-  });
-
   it('documents the eight action endpoints: snapshot on 200, Error on their 4xx paths', () => {
     // The spec object is a literal type; these helpers view it as plain JSON.
     const post = (p: string) =>