feat(ui): 添加底部状态栏和优化代码编辑器空状态

- 新增 StatusBar 组件，显示 Git 分支、诊断信息和连接状态
- 添加 Git API 端点 (GET /api/files/git) 获取分支和 dirty 状态
- 优化 CodeEditor 空状态，添加图标和引导提示
- 修复 Chat 页面高度问题 (h-screen -> h-full)

packages/server/src/routes/files.ts

@@ -7,8 +7,12 @@
 import { Hono } from 'hono';
 import { readdir, stat, readFile, writeFile, mkdir } from 'node:fs/promises';
 import { join, resolve, basename, extname, dirname } from 'node:path';
+import { exec } from 'node:child_process';
+import { promisify } from 'node:util';
 import { searchFiles as coreSearchFiles, type FileIndexEntry } from '@ai-assistant/core';
 
+const execAsync = promisify(exec);
+
 const filesRouter = new Hono();
 
 // 工作目录 (默认为当前目录)
@@ -444,4 +448,35 @@ filesRouter.put('/write', async (c) => {
   }
 });
 
+// ============================================================================
+// GET /api/files/git - 获取 Git 信息
+// ============================================================================
+filesRouter.get('/git', async (c) => {
+  try {
+    // 获取当前分支
+    const { stdout: branch } = await execAsync('git rev-parse --abbrev-ref HEAD', {
+      cwd: workingDirectory,
+    });
+
+    // 检查是否有未提交的更改
+    const { stdout: status } = await execAsync('git status --porcelain', {
+      cwd: workingDirectory,
+    });
+
+    return c.json({
+      success: true,
+      data: {
+        branch: branch.trim(),
+        dirty: status.trim().length > 0,
+      },
+    });
+  } catch {
+    // 可能不是 Git 仓库
+    return c.json({
+      success: true,
+      data: null,
+    });
+  }
+});
+
 export { filesRouter };