refactor: separate application UI state owners

src/cctvFocusRequest.test.mjs

@@ -1,3 +1,4 @@
+import { readShellSource } from './testSupport/readShellSource.mjs';
 import test from 'node:test';
 import assert from 'node:assert/strict';
 import { readFileSync } from 'node:fs';
@@ -57,7 +58,7 @@ test('UI CCTV focus listener registration disposes the exact added callback once
   assert.strictEqual(added[0].callback, listener);
   assert.strictEqual(removed[0].callback, added[0].callback);
 
-  const uiSource = readFileSync(new URL('./ui/applicationShell.js', import.meta.url), 'utf8');
+  const uiSource = readShellSource();
   assert.match(
     uiSource,
     /_removeCctvRequestFocusListener = registerCctvFocusRequestListener\([\s\S]+this\._cctvRequestFocusHandler/,