refactor(main): extract remaining inline runtime logic from main

src/main/runtime/composers/stats-startup-composer.test.ts

@@ -0,0 +1,23 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { composeStatsStartupRuntime } from './stats-startup-composer';
+
+test('composeStatsStartupRuntime returns stats startup handlers', async () => {
+  const composed = composeStatsStartupRuntime({
+    ensureStatsServerStarted: () => 'http://127.0.0.1:8766',
+    ensureBackgroundStatsServerStarted: () => ({
+      url: 'http://127.0.0.1:8766',
+      runningInCurrentProcess: true,
+    }),
+    stopBackgroundStatsServer: async () => ({ ok: true, stale: false }),
+    ensureImmersionTrackerStarted: () => {},
+  });
+
+  assert.equal(composed.ensureStatsServerStarted(), 'http://127.0.0.1:8766');
+  assert.deepEqual(composed.ensureBackgroundStatsServerStarted(), {
+    url: 'http://127.0.0.1:8766',
+    runningInCurrentProcess: true,
+  });
+  assert.deepEqual(await composed.stopBackgroundStatsServer(), { ok: true, stale: false });
+  assert.equal(typeof composed.ensureImmersionTrackerStarted, 'function');
+});