Vendor Chatwoot Vue 3 frontend into frontend/

Copy the Chatwoot (v4.14.0) frontend runnable subset into frontend/ for
customization:
- app/javascript/ (Vue SPA: dashboard, widget, sdk, portal, superadmin)
- app/views/ (ERB templates for vite-plugin-ruby entrypoint resolution)
- app/helpers/, app/assets/ (Rails view helpers, static assets)
- enterprise/ (Enterprise edition frontend overlay)
- config/vite.json, vite.config.ts, bin/vite (Vite-Rails toolchain)
- package.json, pnpm-lock.yaml, tailwind/postcss/eslint configs
- Gemfile, Gemfile.lock (vite_rails gem for bin/vite binstub)

Excluded Rails backend: controllers, models, services, jobs, mailers,
policies, db, lib, spec, public, node_modules.

Update references to the new frontend location:
- .gitignore: exclude frontend build artifacts (node_modules, tmp, packs),
  keep frontend/bin/ and frontend/vendor/ via negation
- backend/scripts/parity_frontend_smoke.sh: CHATWOOT_DIR default
  reference/chatwoot -> ../frontend
- backend/scripts/parity_frontend_browser_smoke.mjs: same default update
- AGENTS.md: add frontend section with Rails/Vite coupling notes
- README: architecture tree includes frontend/

frontend/app/javascript/widget/composables/specs/useDarkMode.spec.js

@@ -0,0 +1,49 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { useDarkMode } from '../useDarkMode';
+import { useMapGetter } from 'dashboard/composables/store';
+
+vi.mock('dashboard/composables/store', () => ({
+  useMapGetter: vi.fn(),
+}));
+
+describe('useDarkMode', () => {
+  let mockDarkMode;
+
+  beforeEach(() => {
+    mockDarkMode = { value: 'light' };
+    vi.mocked(useMapGetter).mockReturnValue(mockDarkMode);
+  });
+
+  it('returns darkMode, prefersDarkMode', () => {
+    const result = useDarkMode();
+    expect(result).toHaveProperty('darkMode');
+    expect(result).toHaveProperty('prefersDarkMode');
+  });
+
+  describe('prefersDarkMode', () => {
+    it('returns false when darkMode is light', () => {
+      const { prefersDarkMode } = useDarkMode();
+      expect(prefersDarkMode.value).toBe(false);
+    });
+
+    it('returns true when darkMode is dark', () => {
+      mockDarkMode.value = 'dark';
+      const { prefersDarkMode } = useDarkMode();
+      expect(prefersDarkMode.value).toBe(true);
+    });
+
+    it('returns true when darkMode is auto and OS prefers dark mode', () => {
+      mockDarkMode.value = 'auto';
+      vi.spyOn(window, 'matchMedia').mockReturnValue({ matches: true });
+      const { prefersDarkMode } = useDarkMode();
+      expect(prefersDarkMode.value).toBe(true);
+    });
+
+    it('returns false when darkMode is auto and OS prefers light mode', () => {
+      mockDarkMode.value = 'auto';
+      vi.spyOn(window, 'matchMedia').mockReturnValue({ matches: false });
+      const { prefersDarkMode } = useDarkMode();
+      expect(prefersDarkMode.value).toBe(false);
+    });
+  });
+});