feat(engine): 添加运行时上下文支持并重构工具迭代限制

添加 RuntimeContext 类用于捕获模型运行时的日期时间信息，
包括UTC时间、本地时间和时区信息，并在系统提示中显示这些信息。

同时增加最大上下文消息数和工具迭代次数的配置选项，
将验证服务从引擎加载器中移除，并更新相关的数据结构和接口。

BREAKING CHANGE: 移除了验证服务，相关字段被替换为证据状态和接受状态。

- 添加 RuntimeContext 类和相关渲染方法
- 增加 max_context_messages 和 max_tool_iterations 配置
- 移除 ValidationService 相关代码
- 更新消息记录中的验证状态字段
- 添加原始工具调用检测和回退处理

app-instance/frontend/lib/api.ts

@@ -271,7 +271,7 @@ export async function sendMessage(
   run_id?: string;
   task_id?: string | null;
   task_status?: string | null;
-  validation_result?: Record<string, unknown> | null;
+  evidence_status?: string | null;
 }> {
   const body: Record<string, unknown> = { message, session_id: sessionId };
   if (attachments && attachments.length > 0) {
@@ -293,7 +293,7 @@ export async function sendMessage(
     finish_reason?: string;
     task_id?: string | null;
     task_status?: string | null;
-    validation_result?: Record<string, unknown> | null;
+    evidence_status?: string | null;
   }>('/api/chat', {
     method: 'POST',
     body: JSON.stringify(body),
@@ -305,28 +305,29 @@ export async function sendMessage(
     run_id: result.run_id,
     task_id: result.task_id,
     task_status: result.task_status,
-    validation_result: result.validation_result,
+    evidence_status: result.evidence_status,
   };
 }
 
 export async function submitChatFeedback(params: {
   sessionId: string;
   runId: string;
-  feedbackType: 'satisfied' | 'revise' | 'abandon';
+  feedbackType: 'accept' | 'revise' | 'abandon';
   comment?: string;
 }): Promise<{
   session_id: string;
   run_id: string;
   task_id: string;
   task_status: string;
+  acceptance_type: string;
   feedback_type: string;
 }> {
-  return fetchJSON('/api/chat/feedback', {
+  return fetchJSON('/api/chat/acceptance', {
     method: 'POST',
     body: JSON.stringify({
       session_id: params.sessionId,
       run_id: params.runId,
-      feedback_type: params.feedbackType,
+      acceptance_type: params.feedbackType,
       comment: params.comment,
     }),
   });

app-instance/frontend/lib/chat-messages.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 
-import { getTaskCardMessageIndexes, mergeServerWithPendingUsers, shouldMergePendingUsers } from '@/lib/chat-messages';
+import { getTaskCardMessageIndexes, mergeServerWithPendingUsers, shouldDisplayChatMessage, shouldMergePendingUsers } from '@/lib/chat-messages';
 import type { ChatMessage } from '@/types';
 
 describe('chat message helpers', () => {
@@ -85,10 +85,17 @@ describe('chat message helpers', () => {
         content: 'Final answer.',
         run_id: 'run-1',
         task_id: 'task-1',
-        task_status: 'awaiting_feedback',
+        task_status: 'awaiting_acceptance',
       },
     ];
 
     expect(Array.from(getTaskCardMessageIndexes(messages))).toEqual([2]);
   });
+
+  it('hides empty assistant records from session history', () => {
+    expect(shouldDisplayChatMessage({ role: 'assistant', content: '', task_id: 'task-1', run_id: 'run-1' })).toBe(false);
+    expect(shouldDisplayChatMessage({ role: 'assistant', content: '\u200B\uFEFF', task_id: 'task-1', run_id: 'run-1' })).toBe(false);
+    expect(shouldDisplayChatMessage({ role: 'assistant', content: 'Final answer.', task_id: 'task-1', run_id: 'run-1' })).toBe(true);
+    expect(shouldDisplayChatMessage({ role: 'user', content: '' })).toBe(true);
+  });
 });

app-instance/frontend/lib/chat-messages.ts

@@ -1,5 +1,28 @@
 import type { ChatMessage } from '@/types';
 
+const INVISIBLE_CONTENT_CHARS = /[\u200B-\u200D\uFEFF]/g;
+
+export function normalizedMessageText(content: unknown): string {
+  if (typeof content === 'string') {
+    return content.replace(INVISIBLE_CONTENT_CHARS, '').trim();
+  }
+  if (content == null) {
+    return '';
+  }
+  return String(content).replace(INVISIBLE_CONTENT_CHARS, '').trim();
+}
+
+export function hasVisibleChatContent(msg: ChatMessage): boolean {
+  if (normalizedMessageText(msg.content)) {
+    return true;
+  }
+  return Boolean(msg.attachments?.length);
+}
+
+export function shouldDisplayChatMessage(msg: ChatMessage): boolean {
+  return msg.role !== 'assistant' || hasVisibleChatContent(msg);
+}
+
 export function messageFingerprint(msg: ChatMessage): string {
   const attachmentKey = (msg.attachments ?? [])
     .map((a) => `${a.file_id ?? ''}:${a.name}:${a.content_type}:${a.size ?? ''}`)