feat(ui): 权限确认对话框支持 Diff 预览

- 添加 Diff 按钮，点击可展开/折叠文件变更预览
- Server 端生成 diff 信息并传递到前端
- 默认折叠，用户可按需查看

packages/server/src/permission/handler.ts

@@ -9,6 +9,8 @@ import type {
   PermissionRequestPayload,
   PermissionDisplayContext,
   ServerMessage,
+  DiffInfo,
+  DiffHunkInfo,
 } from '../types.js';
 import { inferPermissionType } from '@ai-assistant/core';
 import type { PermissionDecision, PermissionContext, PermissionType } from '@ai-assistant/core';
@@ -79,6 +81,73 @@ function isAutoApproved(sessionId: string, ctx: PermissionContext): boolean {
   return false;
 }
 
+/**
+ * 生成简单的行级别 diff 信息
+ * 用于在权限确认对话框中显示文件变更预览
+ */
+function generateDiffInfo(oldContent: string | undefined, newContent: string | undefined): DiffInfo | undefined {
+  // 如果没有内容，无法生成 diff
+  if (newContent === undefined) {
+    return undefined;
+  }
+
+  const isNew = !oldContent;
+  const oldLines = oldContent ? oldContent.split('\n') : [];
+  const newLines = newContent.split('\n');
+
+  // 简单的行级别 diff
+  const lines: DiffHunkInfo['lines'] = [];
+  let additions = 0;
+  let deletions = 0;
+
+  if (isNew) {
+    // 新文件：所有行都是添加
+    newLines.forEach((line, index) => {
+      lines.push({
+        type: 'add',
+        lineNumber: index + 1,
+        content: line,
+      });
+      additions++;
+    });
+  } else {
+    // 编辑：显示删除和添加
+    // 对于 edit_file（search-replace），oldContent 是被替换的部分，newContent 是替换后的部分
+    oldLines.forEach((line, index) => {
+      lines.push({
+        type: 'remove',
+        lineNumber: index + 1,
+        content: line,
+      });
+      deletions++;
+    });
+    newLines.forEach((line, index) => {
+      lines.push({
+        type: 'add',
+        lineNumber: index + 1,
+        content: line,
+      });
+      additions++;
+    });
+  }
+
+  // 构建单个 hunk
+  const hunk: DiffHunkInfo = {
+    oldStart: 1,
+    oldCount: oldLines.length,
+    newStart: 1,
+    newCount: newLines.length,
+    lines,
+  };
+
+  return {
+    isNew,
+    additions,
+    deletions,
+    hunks: [hunk],
+  };
+}
+
 /**
  * 构建权限请求显示上下文
  * 将 Core 的完整 PermissionContext 转换为用于前端显示的精简格式
@@ -135,11 +204,18 @@ export function createServerPermissionCallback(sessionId: string) {
     const permissionType = inferPermissionType(permCtx);
     const context = buildDisplayContext(permCtx);
 
+    // 为文件操作生成 diff
+    let diff: DiffInfo | undefined;
+    if (permissionType === 'file' && (permCtx.fileOperation === 'write' || permCtx.fileOperation === 'edit')) {
+      diff = generateDiffInfo(permCtx.oldContent, permCtx.newContent);
+    }
+
     // 构建请求 payload
     const payload: PermissionRequestPayload = {
       requestId,
       permissionType,
       context,
+      diff,
     };
 
     // 发送权限请求到客户端

packages/ui/src/components/PermissionDialog.tsx

@@ -15,6 +15,9 @@ import {
   X,
   Check,
   AlertTriangle,
+  ChevronDown,
+  ChevronUp,
+  Diff,
 } from 'lucide-react';
 import { motion, AnimatePresence } from 'framer-motion';
 import { cn } from '../utils/cn';
@@ -166,6 +169,7 @@ export function PermissionDialog({
   responsive = false,
 }: PermissionDialogProps) {
   const [remember, setRemember] = useState(false);
+  const [showDiff, setShowDiff] = useState(false);
   const { requestId, permissionType, context, diff } = request;
 
   const handleAllow = () => {
@@ -205,22 +209,39 @@ export function PermissionDialog({
       case 'file':
         return (
           <div className="space-y-2">
-            <div className="flex items-center gap-2 text-sm">
-              <span className="text-fg-muted">Operation:</span>
-              <span className={cn(
-                'px-2 py-0.5 rounded text-xs font-medium',
-                context.operation === 'delete' ? 'bg-red-500/20 text-red-400' :
-                context.operation === 'write' ? 'bg-yellow-500/20 text-yellow-400' :
-                'bg-blue-500/20 text-blue-400'
-              )}>
-                {context.operation?.toUpperCase()}
-              </span>
+            <div className="flex items-center justify-between">
+              <div className="flex items-center gap-2 text-sm">
+                <span className="text-fg-muted">Operation:</span>
+                <span className={cn(
+                  'px-2 py-0.5 rounded text-xs font-medium',
+                  context.operation === 'delete' ? 'bg-red-500/20 text-red-400' :
+                  context.operation === 'write' ? 'bg-yellow-500/20 text-yellow-400' :
+                  'bg-blue-500/20 text-blue-400'
+                )}>
+                  {context.operation?.toUpperCase()}
+                </span>
+              </div>
+              {diff && (
+                <button
+                  onClick={() => setShowDiff(!showDiff)}
+                  className={cn(
+                    'flex items-center gap-1.5 px-2 py-1 rounded text-xs font-medium transition-colors',
+                    showDiff
+                      ? 'bg-blue-500/20 text-blue-400'
+                      : 'bg-surface-base text-fg-muted hover:text-fg-default hover:bg-surface-emphasis'
+                  )}
+                >
+                  <Diff size={14} />
+                  <span>Diff</span>
+                  {showDiff ? <ChevronUp size={14} /> : <ChevronDown size={14} />}
+                </button>
+              )}
             </div>
             <div className="text-sm text-fg-muted">Path:</div>
             <code className="block px-3 py-2 bg-surface-base rounded-lg font-mono text-sm text-blue-300 break-all">
               {context.path}
             </code>
-            {diff && <DiffViewer diff={diff} />}
+            {diff && showDiff && <DiffViewer diff={diff} />}
           </div>
         );