refactor: extract application construction and lifecycle

src/app/startupCamera.test.mjs

@@ -0,0 +1,17 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { flyToAustin } from '../camera.js';
+
+test('teardown before the initial camera delay prevents a late flight', (t) => {
+  t.mock.timers.enable({ apis: ['setTimeout'] });
+  let flights = 0;
+  let cancelled = 0;
+  const stop = flyToAustin({
+    isDestroyed: () => false,
+    camera: { setView() {}, flyTo() { flights++; }, cancelFlight() { cancelled++; } },
+  });
+  stop();
+  t.mock.timers.tick(1000);
+  assert.equal(flights, 0);
+  assert.equal(cancelled, 1);
+});