refactor: 聊天室 Agent 重构 — ToolLoopAgent + 论坛式布局

后端:
- 删除 agent-stream.ts，新建 alfred-agent.ts (ToolLoopAgent 工厂)
- 新建 get-current-time.ts 工具 (zod schema)
- 重构 send.ts: createAgentUIStreamResponse + onFinish 可靠持久化

前端:
- 删除 MessageBubble.tsx，新建 ToolCallCard.tsx (四态)
- 重构 ChatPanel.tsx: 论坛式 Card 布局 + PartRenderer 分派
- 移除 @ant-design/x 依赖，改用 antd 组件 + streamdown

依赖:
+ zod + streamdown
- @ant-design/x - @ant-design/x-markdown

测试: 306 pass, typecheck/lint 0 errors

src/server/routes/chat/send.ts

@@ -1,10 +1,15 @@
 import type Database from "bun:sqlite";
 
-import type { RuntimeMode } from "../../../shared/api";
-import type { IncomingMessage } from "../../ai/agent-stream";
+import { createAgentUIStreamResponse, type UIMessage } from "ai";
+import { eq } from "drizzle-orm";
 
-import { agentStream, extractTextContent } from "../../ai/agent-stream";
+import type { RuntimeMode } from "../../../shared/api";
+
+import { createAlfredAgent } from "../../ai/agents/alfred-agent";
+import { buildProviderRegistry } from "../../ai/registry";
+import { wrap } from "../../db/connection";
 import { createMessage, getConversation, updateConversationTimestamp } from "../../db/conversations";
+import { models, providers } from "../../db/schema";
 import { createApiError, jsonResponse } from "../../helpers";
 import { validateIdParam } from "../../middleware";
 
@@ -15,7 +20,7 @@ export async function handleSendChat(req: Request, db: Database, mode: RuntimeMo
   const validated = validateIdParam(projectId ?? "", mode);
   if (validated instanceof Response) return validated;
 
-  let body: { conversationId?: string; messages?: IncomingMessage[] };
+  let body: { conversationId?: string; messages?: UIMessage[] };
   try {
     body = (await req.json()) as typeof body;
   } catch {
@@ -46,44 +51,62 @@ export async function handleSendChat(req: Request, db: Database, mode: RuntimeMo
     return jsonResponse(createApiError("会话不属于该项目", 403), { mode, status: 403 });
   }
 
-  for (const msg of body.messages ?? []) {
+  const lastMsg = body.messages[body.messages.length - 1];
+  if (lastMsg?.role === "user") {
+    const content =
+      lastMsg.parts
+        ?.filter((p) => p.type === "text")
+        .map((p) => p.text)
+        .join("") ?? "";
     createMessage(db, {
-      content: extractTextContent(msg),
+      content,
       conversationId: conversation.id,
-      role: (msg.role ?? "user") as "assistant" | "system" | "user",
+      parts: JSON.stringify(lastMsg.parts ?? []),
+      role: "user",
     });
   }
 
   updateConversationTimestamp(db, conversation.id);
 
+  let model;
   try {
-    const result = agentStream({
-      db,
-      messages: body.messages,
-      modelDbId: conversation.modelId,
+    const d = wrap(db);
+    const modelRow = d.select().from(models).where(eq(models.id, conversation.modelId)).get();
+    if (!modelRow) {
+      return jsonResponse(createApiError(`模型不存在: ${conversation.modelId}`, 500), { mode, status: 500 });
+    }
+
+    const providerRow = d.select().from(providers).where(eq(providers.id, modelRow.providerId)).get();
+    if (!providerRow) {
+      return jsonResponse(createApiError(`供应商不存在: ${modelRow.providerId}`, 500), { mode, status: 500 });
+    }
+
+    const registry = buildProviderRegistry(db);
+    model = registry.languageModel(`${providerRow.id}:${modelRow.modelId}`);
+  } catch (e: unknown) {
+    const msg = e instanceof Error ? e.message : String(e);
+    return jsonResponse(createApiError(`模型初始化失败：${msg}`, 500), { mode, status: 500 });
+  }
+
+  try {
+    const agent = createAlfredAgent(model);
+    return await createAgentUIStreamResponse({
+      agent,
+      onFinish: ({ responseMessage }) => {
+        const text = responseMessage.parts
+          .filter((p): p is { text: string; type: "text" } => p.type === "text")
+          .map((p) => p.text)
+          .join("");
+        createMessage(db, {
+          content: text,
+          conversationId: conversation.id,
+          parts: JSON.stringify(responseMessage.parts),
+          role: "assistant",
+        });
+        updateConversationTimestamp(db, conversation.id);
+      },
+      uiMessages: body.messages,
     });
-
-    const stream = result.toUIMessageStreamResponse();
-
-    const saveReply = async () => {
-      try {
-        const fullContent = await result.text;
-        if (fullContent) {
-          createMessage(db, {
-            content: fullContent,
-            conversationId: conversation.id,
-            role: "assistant",
-          });
-          updateConversationTimestamp(db, conversation.id);
-        }
-      } catch {
-        // stream ended without content, nothing to persist
-      }
-    };
-
-    void saveReply();
-
-    return stream;
   } catch (e: unknown) {
     const msg = e instanceof Error ? e.message : String(e);
     return jsonResponse(createApiError(`AI 调用失败：${msg}`, 500), { mode, status: 500 });