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.ts

@@ -37,7 +37,7 @@ export const openApiSpec = {
       get: {
         summary: 'Game state snapshot',
         description:
-          'Full current game state for client polling — account, sim clock, planes and packages, plus the static market reference data (catalog + economy constants) so clients can compute buy/sell previews locally. Tick-on-read: each call first advances the sim clock by (real time since last read) × timeScale (clamped per tick), so expiry/delivery/spawn are always applied before the snapshot is returned.',
+          'Full current game state for client polling — account, sim clock, planes and packages, plus the static market reference data (catalog + economy constants) so clients can compute buy/sell previews locally. The world clock advances on a ~1 s background tick at a fixed rate (v0.52.0, ISS-117: no player-facing time controls), clamped per tick; while no plane is flying or in repair the clock stays frozen. Each call ticks first, so expiry/delivery/spawn are always applied before the snapshot is returned.',
         operationId: 'getState',
         responses: {
           200: {
@@ -51,40 +51,6 @@ export const openApiSpec = {
         },
       },
     },
-    '/api/sim': {
-      post: {
-        summary: 'Set sim time controls',
-        description:
-          'Advance the sim clock (tick-on-read) and set the time scale / pause state. The clock is advanced first, so the returned simState already reflects current game time; package expiry, arrival delivery and market spawn run inside that tick.',
-        operationId: 'setSimControls',
-        requestBody: {
-          required: false,
-          content: {
-            'application/json': {
-              schema: { $ref: '#/components/schemas/SimControlsRequest' },
-            },
-          },
-        },
-        responses: {
-          200: {
-            description: 'Updated sim state',
-            content: {
-              'application/json': {
-                schema: { $ref: '#/components/schemas/SimState' },
-              },
-            },
-          },
-          400: {
-            description: 'Invalid body (not an object, unknown field, or wrong types)',
-            content: {
-              'application/json': {
-                schema: { $ref: '#/components/schemas/Error' },
-              },
-            },
-          },
-        },
-      },
-    },
     '/api/version': {
       get: {
         summary: 'App version',
@@ -493,24 +459,9 @@ export const openApiSpec = {
       SimState: {
         type: 'object',
         properties: {
-          clockMs: { type: 'integer', description: 'Sim-clock epoch ms (game time)' },
-          timeScale: { type: 'number', minimum: 1, maximum: 1000 },
-          paused: { type: 'boolean' },
-        },
-        required: ['clockMs', 'timeScale', 'paused'],
-      },
-      SimControlsRequest: {
-        type: 'object',
-        description: 'Partial update — omit a field to leave it unchanged.',
-        properties: {
-          timeScale: {
-            type: 'number',
-            minimum: 1,
-            maximum: 1000,
-            description: 'Game-time multiplier; values outside [1, 1000] are clamped. The UI offers the ladder 1/2/5/10/25/50/100/250/500/1000.',
-          },
-          paused: { type: 'boolean' },
+          clockMs: { type: 'integer', description: 'Sim-clock epoch ms (game time). The world runs at a fixed rate with no player-facing controls (v0.52.0, ISS-117).' },
         },
+        required: ['clockMs'],
       },
       LoadPackageRequest: {
         type: 'object',