fix: 扩展模型消息内容块数组配置

- 升级高级设置为消息级格式并兼容旧 system 配置

- 增加 VLM 图片首轮与文本追问的多轮连接验证

easyflow-ui-admin/app/src/views/ai/model/AddModelModal.vue

@@ -34,11 +34,11 @@ import {
 import { resetModelAbility } from '#/views/ai/model/modelUtils/model-ability-utils';
 
 type AgentHttpVersionPolicy = 'AUTO' | 'HTTP_1_1' | 'HTTP_2_PREFERRED';
-type AgentSystemContentFormat = 'STRING' | 'TEXT_PARTS';
+type AgentMessageContentFormat = 'STANDARD' | 'TEXT_PARTS';
 
 interface ModelOptions {
   agentHttpVersionPolicy: AgentHttpVersionPolicy;
-  agentSystemContentFormat: AgentSystemContentFormat;
+  agentMessageContentFormat: AgentMessageContentFormat;
   [key: string]: unknown;
 }
 
@@ -116,7 +116,7 @@ const formData = reactive<FormData>({
   supportToolMessage: null,
   options: {
     agentHttpVersionPolicy: 'AUTO',
-    agentSystemContentFormat: 'STRING',
+    agentMessageContentFormat: 'STANDARD',
   },
 });
 
@@ -126,8 +126,8 @@ const agentHttpVersionOptions = [
   { label: 'HTTP/2 优先', value: 'HTTP_2_PREFERRED' },
 ] as const;
 
-const agentSystemContentFormatOptions = [
-  { label: '字符串（默认）', value: 'STRING' },
+const agentMessageContentFormatOptions = [
+  { label: '标准格式（默认）', value: 'STANDARD' },
   { label: '内容块数组', value: 'TEXT_PARTS' },
 ] as const;
 
@@ -140,10 +140,10 @@ const normalizeAgentHttpVersionPolicy = (
   return 'AUTO';
 };
 
-const normalizeAgentSystemContentFormat = (
+const normalizeAgentMessageContentFormat = (
   value?: unknown,
-): AgentSystemContentFormat => {
-  return value === 'TEXT_PARTS' ? 'TEXT_PARTS' : 'STRING';
+): AgentMessageContentFormat => {
+  return value === 'TEXT_PARTS' ? 'TEXT_PARTS' : 'STANDARD';
 };
 
 const normalizeModelOptions = (options?: unknown): ModelOptions => {
@@ -151,14 +151,25 @@ const normalizeModelOptions = (options?: unknown): ModelOptions => {
     options && typeof options === 'object' && !Array.isArray(options)
       ? (options as Record<string, unknown>)
       : {};
+  const {
+    agentSystemContentFormat: legacyMessageContentFormat,
+    ...currentOptions
+  } = source;
+  const currentMessageContentFormat = source.agentMessageContentFormat;
+  const messageContentFormat =
+    currentMessageContentFormat === null ||
+    currentMessageContentFormat === undefined ||
+    (typeof currentMessageContentFormat === 'string' &&
+      currentMessageContentFormat.trim() === '')
+      ? legacyMessageContentFormat
+      : currentMessageContentFormat;
   return {
-    ...source,
+    ...currentOptions,
     agentHttpVersionPolicy: normalizeAgentHttpVersionPolicy(
       source.agentHttpVersionPolicy,
     ),
-    agentSystemContentFormat: normalizeAgentSystemContentFormat(
-      source.agentSystemContentFormat,
-    ),
+    agentMessageContentFormat:
+      normalizeAgentMessageContentFormat(messageContentFormat),
   };
 };
 
@@ -592,13 +603,13 @@ const save = async () => {
                   />
                 </ElSelect>
               </ElFormItem>
-              <ElFormItem label="System 消息格式">
+              <ElFormItem label="消息内容格式">
                 <ElSelect
-                  v-model="formData.options.agentSystemContentFormat"
-                  aria-label="System 消息格式"
+                  v-model="formData.options.agentMessageContentFormat"
+                  aria-label="消息内容格式"
                 >
                   <ElOption
-                    v-for="item in agentSystemContentFormatOptions"
+                    v-for="item in agentMessageContentFormatOptions"
                     :key="item.value"
                     :label="item.label"
                     :value="item.value"