feat: 添加文件写入 diff 预览和 LSP 诊断优化

- 文件写入/编辑前显示 diff 对比供用户确认
- LSP 诊断只显示错误和警告，忽略 hint/info
- 优化 LSP 等待时间：首次启动 2s，后续 300ms

src/tools/filesystem/edit_file.ts

@@ -42,32 +42,11 @@ export const editFileTool: ToolWithMetadata = {
       ? filePath
       : path.join(cwd, filePath);
 
-    // 权限检查
-    const permissionManager = getPermissionManager();
-    const permResult = await permissionManager.checkFilePermission({
-      operation: 'edit',
-      path: absolutePath,
-      workdir: cwd,
-    });
-
-    if (!permResult.allowed) {
-      if (permResult.needsConfirmation) {
-        return {
-          success: false,
-          output: '',
-          error: `需要用户确认: 编辑 ${absolutePath}\n原因: ${permResult.reason || '需要权限确认'}`,
-        };
-      }
-      return {
-        success: false,
-        output: '',
-        error: `权限被拒绝: ${permResult.reason || '不允许编辑此文件'}`,
-      };
-    }
-
     try {
+      // 先读取文件内容，用于验证和 diff 显示
       const content = await fs.readFile(absolutePath, 'utf-8');
 
+      // 验证 old_string 是否存在且唯一
       if (!content.includes(oldString)) {
         return {
           success: false,
@@ -85,6 +64,31 @@ export const editFileTool: ToolWithMetadata = {
         };
       }
 
+      // 权限检查（传递内容用于 diff 显示）
+      const permissionManager = getPermissionManager();
+      const permResult = await permissionManager.checkFilePermission({
+        operation: 'edit',
+        path: absolutePath,
+        workdir: cwd,
+        oldContent: oldString,
+        newContent: newString,
+      });
+
+      if (!permResult.allowed) {
+        if (permResult.needsConfirmation) {
+          return {
+            success: false,
+            output: '',
+            error: `需要用户确认: 编辑 ${absolutePath}\n原因: ${permResult.reason || '需要权限确认'}`,
+          };
+        }
+        return {
+          success: false,
+          output: '',
+          error: `权限被拒绝: ${permResult.reason || '不允许编辑此文件'}`,
+        };
+      }
+
       const newContent = content.replace(oldString, newString);
       await fs.writeFile(absolutePath, newContent, 'utf-8');
 

src/tools/filesystem/write_file.ts

@@ -36,12 +36,13 @@ export const writeFileTool: ToolWithMetadata = {
       ? filePath
       : path.join(cwd, filePath);
 
-    // 权限检查
+    // 权限检查（传递内容用于 diff 显示）
     const permissionManager = getPermissionManager();
     const permResult = await permissionManager.checkFilePermission({
       operation: 'write',
       path: absolutePath,
       workdir: cwd,
+      newContent: content,
     });
 
     if (!permResult.allowed) {