refactor: extract application construction and lifecycle

src/app/mapLifecycle.test.mjs

@@ -0,0 +1,40 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { MapStackController } from '../mapStackController.js';
+import {
+  installRenderGovernor, uninstallRenderGovernor,
+  holdContinuousRender, governorRequestRender, getRenderGovernorDiagnostics,
+} from '../renderGovernor.js';
+
+test('destroy invalidates a pending imagery provider before it can touch the viewer', async () => {
+  let resolveProvider;
+  let removed = 0;
+  const changes = [];
+  const controller = new MapStackController({}, { onChange: (state) => changes.push(state.status) });
+  controller._getImageryProvider = () => new Promise((resolve) => { resolveProvider = resolve; });
+  controller._removeImageryErrorListener = () => { removed++; };
+  const switching = controller.setStack('osm');
+  controller.destroy();
+  resolveProvider({ provider: {} });
+  await switching;
+  assert.equal(removed, 1);
+  assert.deepEqual(changes, ['switching']);
+  await controller.setStack('osm');
+  controller.destroy();
+  assert.equal(removed, 1);
+});
+
+test('uninstall only releases the current viewer and makes later render requests inactive', () => {
+  let renders = 0;
+  const viewer = { scene: { requestRender: () => { renders++; } } };
+  installRenderGovernor(viewer);
+  holdContinuousRender('fixture');
+  uninstallRenderGovernor({});
+  assert.equal(getRenderGovernorDiagnostics().installed, true);
+  uninstallRenderGovernor(viewer);
+  const before = renders;
+  governorRequestRender('late');
+  assert.equal(renders, before);
+  assert.equal(getRenderGovernorDiagnostics().installed, false);
+  assert.deepEqual(getRenderGovernorDiagnostics().holds, []);
+});