feat(chat): add paste and drag-drop file upload support

- Add clipboard paste handler for images and files (Ctrl+V / Cmd+V)
- Add drag-and-drop zone with visual feedback
- Update placeholder text to inform users about new features
- Improve file upload UX with drop overlay

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/web-client/src/features/chat/presentation/components/InputArea.tsx

@@ -1,5 +1,5 @@
-import { useState, useRef, useEffect, KeyboardEvent, ChangeEvent } from 'react';
-import { Send, Paperclip, X, Image, FileText, Loader2 } from 'lucide-react';
+import { useState, useRef, useEffect, KeyboardEvent, ChangeEvent, ClipboardEvent, DragEvent } from 'react';
+import { Send, Paperclip, X, Image, FileText, Loader2, Upload } from 'lucide-react';
 import { clsx } from 'clsx';
 import { FileAttachment } from '../stores/chatStore';
 
@@ -49,8 +49,10 @@ export function InputArea({
   uploadProgress = {},
 }: InputAreaProps) {
   const [message, setMessage] = useState('');
+  const [isDragging, setIsDragging] = useState(false);
   const textareaRef = useRef<HTMLTextAreaElement>(null);
   const fileInputRef = useRef<HTMLInputElement>(null);
+  const dropZoneRef = useRef<HTMLDivElement>(null);
 
   // Auto-resize textarea
   useEffect(() => {
@@ -105,6 +107,84 @@ export function InputArea({
     fileInputRef.current?.click();
   };
 
+  // 处理文件验证和添加
+  const processFiles = (files: File[]) => {
+    const validFiles: File[] = [];
+    files.forEach((file) => {
+      if (!ALLOWED_TYPES.includes(file.type)) {
+        console.warn(`不支持的文件类型: ${file.type}`);
+        return;
+      }
+      if (file.size > MAX_FILE_SIZE) {
+        console.warn(`文件过大: ${file.name}`);
+        return;
+      }
+      validFiles.push(file);
+    });
+
+    if (validFiles.length > 0) {
+      onFilesSelected?.(validFiles);
+    }
+  };
+
+  // 处理粘贴事件
+  const handlePaste = (e: ClipboardEvent<HTMLTextAreaElement>) => {
+    const items = e.clipboardData?.items;
+    if (!items) return;
+
+    const files: File[] = [];
+    for (let i = 0; i < items.length; i++) {
+      const item = items[i];
+      if (item.kind === 'file') {
+        const file = item.getAsFile();
+        if (file) {
+          files.push(file);
+        }
+      }
+    }
+
+    if (files.length > 0) {
+      e.preventDefault(); // 阻止默认粘贴行为
+      processFiles(files);
+    }
+  };
+
+  // 拖放事件处理
+  const handleDragEnter = (e: DragEvent) => {
+    e.preventDefault();
+    e.stopPropagation();
+    if (!disabled && !isUploading) {
+      setIsDragging(true);
+    }
+  };
+
+  const handleDragLeave = (e: DragEvent) => {
+    e.preventDefault();
+    e.stopPropagation();
+    // 只有当离开整个drop zone时才取消高亮
+    if (dropZoneRef.current && !dropZoneRef.current.contains(e.relatedTarget as Node)) {
+      setIsDragging(false);
+    }
+  };
+
+  const handleDragOver = (e: DragEvent) => {
+    e.preventDefault();
+    e.stopPropagation();
+  };
+
+  const handleDrop = (e: DragEvent) => {
+    e.preventDefault();
+    e.stopPropagation();
+    setIsDragging(false);
+
+    if (disabled || isUploading) return;
+
+    const files = Array.from(e.dataTransfer?.files || []);
+    if (files.length > 0) {
+      processFiles(files);
+    }
+  };
+
   const formatFileSize = (bytes: number) => {
     if (bytes < 1024) return `${bytes} B`;
     if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
@@ -112,7 +192,27 @@ export function InputArea({
   };
 
   return (
-    <div className="space-y-3">
+    <div
+      ref={dropZoneRef}
+      className={clsx(
+        'space-y-3 relative rounded-xl transition-all',
+        isDragging && 'ring-2 ring-primary-500 ring-offset-2 bg-primary-50',
+      )}
+      onDragEnter={handleDragEnter}
+      onDragLeave={handleDragLeave}
+      onDragOver={handleDragOver}
+      onDrop={handleDrop}
+    >
+      {/* 拖放提示层 */}
+      {isDragging && (
+        <div className="absolute inset-0 z-10 flex items-center justify-center bg-primary-50/90 rounded-xl border-2 border-dashed border-primary-400">
+          <div className="flex flex-col items-center gap-2 text-primary-600">
+            <Upload className="w-8 h-8" />
+            <span className="font-medium">释放以添加文件</span>
+          </div>
+        </div>
+      )}
+
       {/* 文件预览区域 */}
       {pendingFiles.length > 0 && (
         <div className="flex flex-wrap gap-2 px-1">
@@ -208,10 +308,11 @@ export function InputArea({
             value={message}
             onChange={(e) => setMessage(e.target.value)}
             onKeyDown={handleKeyDown}
+            onPaste={handlePaste}
             placeholder={
               pendingFiles.length > 0
                 ? '添加说明文字（可选），或直接发送...'
-                : '输入您的问题...'
+                : '输入您的问题，可粘贴或拖放图片...'
             }
             disabled={disabled || isUploading}
             rows={1}
@@ -244,7 +345,7 @@ export function InputArea({
 
       {/* 提示文字 */}
       <p className="text-xs text-secondary-400 text-center">
-        支持图片 (JPEG, PNG, GIF) 和文档 (PDF, Word, Excel, 文本)，最大 50MB
+        支持粘贴、拖放图片 (JPEG, PNG, GIF) 和文档 (PDF, Word, Excel)，最大 50MB
       </p>
     </div>
   );