feat(ui): 添加文件 Diff 查看功能

当 AI 执行 write_file 或 edit_file 工具时，在工具结果中显示 View Diff 按钮，
点击后在 IDE 面板中显示文件修改前后的对比视图。

主要改动：
- core: edit_file/write_file 工具返回 fileDiff 元数据
- ui: 新增 DiffEditor 组件用于显示文件差异
- ui: ChatMessage 添加 View Diff 按钮
- ui: IDE 组件支持 Diff 视图切换
- ui: useChat hook 处理 fileDiff 回调

pnpm-lock.yaml

@@ -252,6 +252,12 @@ importers:
       '@codemirror/lang-python':
         specifier: ^6.2.1
         version: 6.2.1
+      '@codemirror/merge':
+        specifier: ^6.10.2
+        version: 6.11.2
+      '@codemirror/state':
+        specifier: ^6.5.2
+        version: 6.5.2
       '@codemirror/theme-one-dark':
         specifier: ^6.1.3
         version: 6.1.3
@@ -285,6 +291,9 @@ importers:
       clsx:
         specifier: ^2.1.1
         version: 2.1.1
+      codemirror:
+        specifier: ^6.0.2
+        version: 6.0.2
       framer-motion:
         specifier: ^12.23.26
         version: 12.23.26(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
@@ -1007,6 +1016,9 @@ packages:
   '@codemirror/lint@6.9.2':
     resolution: {integrity: sha512-sv3DylBiIyi+xKwRCJAAsBZZZWo82shJ/RTMymLabAdtbkV5cSKwWDeCgtUq3v8flTaXS2y1kKkICuRYtUswyQ==}
 
+  '@codemirror/merge@6.11.2':
+    resolution: {integrity: sha512-NO5EJd2rLRbwVWLgMdhIntDIhfDtMOKYEZgqV5WnkNUS2oXOCVWLPjG/kgl/Jth2fGiOuG947bteqxP9nBXmMg==}
+
   '@codemirror/search@6.5.11':
     resolution: {integrity: sha512-KmWepDE6jUdL6n8cAAqIpRmLPBZ5ZKnicE8oGU/s3QrAVID+0VhLFrzUucVKHG5035/BSykhExDL/Xm7dHthiA==}
 
@@ -5988,6 +6000,14 @@ snapshots:
       '@codemirror/view': 6.39.4
       crelt: 1.0.6
 
+  '@codemirror/merge@6.11.2':
+    dependencies:
+      '@codemirror/language': 6.11.3
+      '@codemirror/state': 6.5.2
+      '@codemirror/view': 6.39.4
+      '@lezer/highlight': 1.2.3
+      style-mod: 4.1.3
+
   '@codemirror/search@6.5.11':
     dependencies:
       '@codemirror/state': 6.5.2