refactor(ui): own Display control subscriptions and cleanup

src/reasonableDefaults.test.mjs

@@ -246,7 +246,9 @@ test('detection-on-by-default is a default, not an operator override', () => {
   // preset consults the flag, and the detection button sets it.
   assert.match(uiSource, /if \(preset\.detection && !this\._detectionUserOverridden\) \{/,
     'a style preset still yields to an operator who changed detection by hand');
-  const detectionButton = uiBlock("this._detectionBtn.addEventListener('click'", 'cycleDetectionMode()');
+  const displayActions = uiSource.slice(uiSource.indexOf('this._displayControls ='));
+  const detectionButton = displayActions.slice(displayActions.indexOf('cycleDetection:'), displayActions.indexOf('toggleModels:'));
+  assert.match(detectionButton, /cycleDetectionMode\(\)/, 'the button still invokes the detection action');
   assert.match(detectionButton, /this\._detectionUserOverridden = true;/,
     'and the detection control still claims the override when the operator uses it');