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

entrypoints/background.ts

@@ -0,0 +1,105 @@
+import { defineBackground } from 'wxt/sandbox';
+
+export default defineBackground(() => {
+  console.log('LexAI background service worker started');
+
+  // Handle messages from content scripts
+  chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
+    if (message.type === 'ANALYZE_TEXT') {
+      handleAnalyzeText(message.payload).then(sendResponse);
+      return true; // Keep channel open for async response
+    }
+  });
+});
+
+async function handleAnalyzeText(payload: { text: string; action: string }) {
+  try {
+    const config = await chrome.storage.local.get(['provider', 'apiKey', 'model']);
+
+    if (!config.apiKey) {
+      return { error: 'No API key configured. Please open LexAI settings.' };
+    }
+
+    // Route to correct provider
+    switch (config.provider) {
+      case 'openai':
+        return await callOpenAI(payload, config);
+      case 'anthropic':
+        return await callAnthropic(payload, config);
+      case 'groq':
+        return await callGroq(payload, config);
+      default:
+        return { error: 'Unknown provider. Please check settings.' };
+    }
+  } catch (err) {
+    return { error: String(err) };
+  }
+}
+
+async function callOpenAI(payload: { text: string; action: string }, config: any) {
+  const res = await fetch('https://api.openai.com/v1/chat/completions', {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'Authorization': `Bearer ${config.apiKey}`,
+    },
+    body: JSON.stringify({
+      model: config.model || 'gpt-4o-mini',
+      messages: [
+        { role: 'system', content: getSystemPrompt(payload.action) },
+        { role: 'user', content: payload.text },
+      ],
+    }),
+  });
+  const data = await res.json();
+  return { result: data.choices?.[0]?.message?.content };
+}
+
+async function callAnthropic(payload: { text: string; action: string }, config: any) {
+  const res = await fetch('https://api.anthropic.com/v1/messages', {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'x-api-key': config.apiKey,
+      'anthropic-version': '2023-06-01',
+    },
+    body: JSON.stringify({
+      model: config.model || 'claude-3-5-haiku-20241022',
+      max_tokens: 1024,
+      system: getSystemPrompt(payload.action),
+      messages: [{ role: 'user', content: payload.text }],
+    }),
+  });
+  const data = await res.json();
+  return { result: data.content?.[0]?.text };
+}
+
+async function callGroq(payload: { text: string; action: string }, config: any) {
+  const res = await fetch('https://api.groq.com/openai/v1/chat/completions', {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'Authorization': `Bearer ${config.apiKey}`,
+    },
+    body: JSON.stringify({
+      model: config.model || 'llama-3.3-70b-versatile',
+      messages: [
+        { role: 'system', content: getSystemPrompt(payload.action) },
+        { role: 'user', content: payload.text },
+      ],
+    }),
+  });
+  const data = await res.json();
+  return { result: data.choices?.[0]?.message?.content };
+}
+
+function getSystemPrompt(action: string): string {
+  const prompts: Record<string, string> = {
+    grammar: 'You are a grammar checker. Fix grammar, spelling, and punctuation errors in the text. Return only the corrected text without explanations.',
+    rephrase: 'You are a writing assistant. Rephrase the given text to be clearer and more professional. Return only the rephrased text.',
+    tone: 'You are a writing coach. Analyze the tone of the text and suggest improvements. Be concise.',
+    shorten: 'You are an editor. Shorten the text while keeping the key message. Return only the shortened version.',
+    expand: 'You are a writer. Expand the given text with more detail and context. Return only the expanded version.',
+  };
+  return prompts[action] || prompts.grammar;
+}