feat: initial LexAI Chrome extension scaffold

- WXT + React 18 + TypeScript setup
- Background service worker (LLM API proxy)
- Content script (floating toolbar + text selection)
- Options page (provider/model/API key config)
- Popup UI
- Gitea Actions workflows (CI, preview, release)
- Vitest unit tests + Playwright E2E setup
- Supports: OpenAI, Anthropic, Groq, OpenRouter

tests/unit/background.test.ts

@@ -0,0 +1,28 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+describe('Background Service Worker', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('should return error when no API key is configured', async () => {
+    (chrome.storage.local.get as any).mockImplementation((keys: any, cb: any) => cb({}));
+
+    // Simulate the handleAnalyzeText function behavior
+    const config = await new Promise<any>((resolve) =>
+      chrome.storage.local.get(['provider', 'apiKey', 'model'], resolve)
+    );
+
+    expect(config.apiKey).toBeUndefined();
+  });
+
+  it('should store API key correctly', async () => {
+    const testConfig = { provider: 'openai', apiKey: 'sk-test123', model: 'gpt-4o-mini' };
+
+    await new Promise<void>((resolve) =>
+      chrome.storage.local.set(testConfig, resolve)
+    );
+
+    expect(chrome.storage.local.set).toHaveBeenCalledWith(testConfig, expect.any(Function));
+  });
+});