refactor(ai): extract notification logic from js/app.js (agent)

- Moved `showError`, `showStatus`, `showSuccess`, and `updateNotificationPortalVisibility` logic to `js/ui/notificationController.js`.
- Instantiated `NotificationController` in `js/ui/applicationBootstrap.js`.
- Refactored `js/app.js` to delegate notification calls to the controller.
- Added unit tests for `NotificationController`.
- Followed AGENTS.md refactoring checklist.

Co-authored-by: PR0M3TH3AN <[email protected]>

tests/unit/notificationController.test.mjs

@@ -0,0 +1,133 @@
+import { describe, it, beforeEach, afterEach, mock } from 'node:test';
+import assert from 'node:assert';
+import NotificationController from '../../js/ui/notificationController.js';
+
+// Simple mock for HTMLElement
+class MockHTMLElement {
+  constructor() {
+    this.classList = {
+      contains: mock.fn(() => false),
+      add: mock.fn(),
+      remove: mock.fn(),
+      toggle: mock.fn(),
+    };
+    this.textContent = '';
+    this.querySelector = mock.fn(() => null);
+    this.contains = mock.fn(() => false);
+    this.insertBefore = mock.fn();
+    this.remove = mock.fn();
+    this.firstChild = null;
+    this.setAttribute = mock.fn();
+  }
+}
+
+describe('NotificationController', () => {
+  let controller;
+  let mockPortal;
+  let mockErrorContainer;
+  let mockSuccessContainer;
+  let mockStatusContainer;
+  let mockWindow;
+  let mockDocument;
+  let mockUserLogger;
+  let mockDevLogger;
+
+  beforeEach(() => {
+    mockPortal = new MockHTMLElement();
+    mockErrorContainer = new MockHTMLElement();
+    mockSuccessContainer = new MockHTMLElement();
+    mockStatusContainer = new MockHTMLElement();
+
+    mockWindow = {
+      HTMLElement: MockHTMLElement,
+      setTimeout: mock.fn((cb, ms) => setTimeout(cb, ms)),
+      clearTimeout: mock.fn((id) => clearTimeout(id)),
+    };
+
+    mockDocument = {
+        createElement: mock.fn(() => new MockHTMLElement()),
+    };
+
+    mockUserLogger = { error: mock.fn() };
+    mockDevLogger = { log: mock.fn() };
+
+    controller = new NotificationController({
+      portal: mockPortal,
+      errorContainer: mockErrorContainer,
+      successContainer: mockSuccessContainer,
+      statusContainer: mockStatusContainer,
+      loggers: { userLogger: mockUserLogger, devLogger: mockDevLogger },
+      documentRef: mockDocument,
+      windowRef: mockWindow,
+    });
+  });
+
+  afterEach(() => {
+    controller.destroy();
+    mock.reset();
+  });
+
+  it('should instantiate correctly', () => {
+    assert.strictEqual(controller.portal, mockPortal);
+    assert.strictEqual(controller.errorContainer, mockErrorContainer);
+  });
+
+  it('showError should update text content and show container', () => {
+    const msg = 'Test Error';
+    controller.showError(msg);
+
+    assert.strictEqual(mockErrorContainer.textContent, msg);
+    assert.strictEqual(mockErrorContainer.classList.remove.mock.calls.length, 1);
+    assert.strictEqual(mockErrorContainer.classList.remove.mock.calls[0].arguments[0], 'hidden');
+    assert.strictEqual(mockUserLogger.error.mock.calls.length, 1);
+    assert.strictEqual(mockUserLogger.error.mock.calls[0].arguments[0], msg);
+  });
+
+  it('showError should hide container when msg is empty', () => {
+    controller.showError('');
+
+    assert.strictEqual(mockErrorContainer.textContent, '');
+    assert.strictEqual(mockErrorContainer.classList.add.mock.calls.length, 1);
+    assert.strictEqual(mockErrorContainer.classList.add.mock.calls[0].arguments[0], 'hidden');
+  });
+
+  it('updateNotificationPortalVisibility should toggle active class on portal', () => {
+      // Simulate error container being visible
+      mockErrorContainer.classList.contains = mock.fn((cls) => cls !== 'hidden');
+
+      controller.updateNotificationPortalVisibility();
+
+      assert.strictEqual(mockPortal.classList.toggle.mock.calls.length, 1);
+      assert.strictEqual(mockPortal.classList.toggle.mock.calls[0].arguments[0], 'notification-portal--active');
+      assert.strictEqual(mockPortal.classList.toggle.mock.calls[0].arguments[1], true);
+  });
+
+  it('showSuccess should update text content and show container', () => {
+      const msg = 'Success!';
+      controller.showSuccess(msg);
+
+      assert.strictEqual(mockSuccessContainer.textContent, msg);
+      assert.strictEqual(mockSuccessContainer.classList.remove.mock.calls.length, 1);
+      assert.strictEqual(mockSuccessContainer.classList.remove.mock.calls[0].arguments[0], 'hidden');
+  });
+
+  it('showStatus should update text content and show container', () => {
+      const msg = 'Status update';
+      controller.showStatus(msg);
+
+      assert.strictEqual(mockStatusContainer.textContent, msg);
+      assert.strictEqual(mockStatusContainer.classList.remove.mock.calls.length, 1);
+      assert.strictEqual(mockStatusContainer.classList.remove.mock.calls[0].arguments[0], 'hidden');
+  });
+
+  it('showStatus should handle spinner option', () => {
+      const msg = 'Loading...';
+      const mockSpinner = new MockHTMLElement();
+      mockDocument.createElement = mock.fn(() => mockSpinner);
+
+      controller.showStatus(msg, { showSpinner: true });
+
+      assert.strictEqual(mockDocument.createElement.mock.calls.length, 1);
+      assert.strictEqual(mockStatusContainer.insertBefore.mock.calls.length, 1);
+  });
+});