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

playwright.config.ts

@@ -0,0 +1,24 @@
+import { defineConfig } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './tests/e2e',
+  timeout: 30000,
+  use: {
+    // Chrome extension testing
+    channel: 'chrome',
+  },
+  projects: [
+    {
+      name: 'chromium-extension',
+      use: {
+        browserName: 'chromium',
+        launchOptions: {
+          args: [
+            '--disable-extensions-except=.output/chrome-mv3',
+            '--load-extension=.output/chrome-mv3',
+          ],
+        },
+      },
+    },
+  ],
+});