feat: DeepSeek 选择时禁止上传图片附件

DeepSeek 不支持多模态，前端层面阻止用户选择图片文件：

- ChatInput 根据 provider 动态控制 accept 属性(DeepSeek不包含image/*)
- addFiles 中过滤图片文件(DeepSeek自动跳过)
- Paperclip 按钮 Tooltip 区分提示
- provider 切换后即时生效(通过 useAgentStore 响应式读取)

src/components/chat/ChatInput.tsx

@@ -46,6 +46,10 @@ export function ChatInput(): React.JSX.Element {
   const isStreaming = useAgentStore((s) => s.isStreaming);
   const tokenUsage = useAgentStore((s) => s.tokenUsage);
   const currentSessionId = useSessionStore((s) => s.currentSessionId);
+  const provider = useAgentStore((s) => s.provider);
+
+  /** DeepSeek 不支持多模态图片 */
+  const supportsImages = provider !== 'deepseek';
 
   // 草稿自动保存
   useEffect(() => { if (currentSessionId) { const d = sessionStorage.getItem(`draft-${currentSessionId}`); setInput(d ?? ''); } }, [currentSessionId]);
@@ -85,9 +89,21 @@ export function ChatInput(): React.JSX.Element {
 
   const addFiles = useCallback(async (files: FileList | File[]) => {
     const fileArray = Array.from(files).slice(0, 5); // 最多 5 个附件
-    const newAttachments = await Promise.all(fileArray.map(processFile));
+
+    // DeepSeek 不支持多模态，过滤图片
+    const filtered = supportsImages
+      ? fileArray
+      : fileArray.filter((f) => !IMAGE_TYPES.includes(f.type));
+
+    if (filtered.length < fileArray.length && !supportsImages) {
+      // TODO: 用 Toast 提示用户 "DeepSeek 不支持图片，已自动跳过 N 个图片文件"
+    }
+
+    if (filtered.length === 0) return;
+
+    const newAttachments = await Promise.all(filtered.map(processFile));
     setAttachments((prev) => [...prev, ...newAttachments]);
-  }, [processFile]);
+  }, [processFile, supportsImages]);
 
   const removeAttachment = useCallback((id: string) => {
     setAttachments((prev) => prev.filter((a) => a.id !== id));
@@ -224,7 +240,7 @@ export function ChatInput(): React.JSX.Element {
           </div>
         )}
 
-        <input ref={fileInputRef} type="file" multiple accept="image/*,.txt,.md,.json,.csv,.ts,.tsx,.js,.jsx,.py,.rb,.go,.rs,.java,.c,.cpp,.h,.css,.html,.xml,.yaml,.yml,.toml,.ini,.sh,.sql,.log,.pdf" style={{ display: 'none' }} onChange={handleFileChange} />
+        <input ref={fileInputRef} type="file" multiple accept={supportsImages ? 'image/*,.txt,.md,.json,.csv,.ts,.tsx,.js,.jsx,.py,.rb,.go,.rs,.java,.c,.cpp,.h,.css,.html,.xml,.yaml,.yml,.toml,.ini,.sh,.sql,.log,.pdf' : '.txt,.md,.json,.csv,.ts,.tsx,.js,.jsx,.py,.rb,.go,.rs,.java,.c,.cpp,.h,.css,.html,.xml,.yaml,.yml,.toml,.ini,.sh,.sql,.log,.pdf'} style={{ display: 'none' }} onChange={handleFileChange} />
 
         <textarea
           ref={textareaRef} data-chat-input value={input} onChange={handleChange} onKeyDown={handleKeyDown}
@@ -236,7 +252,7 @@ export function ChatInput(): React.JSX.Element {
 
         <Stack direction="row" justifyContent="space-between" alignItems="center" sx={{ mt: 1, minHeight: 32 }}>
           {/* 左侧：附件按钮 */}
-          <Tooltip title="附加文件（图片/文本/代码）">
+          <Tooltip title={supportsImages ? '附加文件（图片/文本/代码）' : '附加文件（文本/代码）— DeepSeek 不支持图片'}>
             <IconButton size="small" sx={{ color: 'text.secondary' }} onClick={handleFileSelect}>
               <Paperclip size={14} />
             </IconButton>