feat: 增加 system 消息格式配置

- 模型管理支持选择字符串或内容块数组格式

- 验证连接携带 system 消息并复用正式运行时模型配置

- 补充配置映射与验证消息角色测试

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

@@ -27,9 +27,11 @@ import {
 } from '#/views/ai/model/modelUtils/model-ability-utils';
 
 type AgentHttpVersionPolicy = 'AUTO' | 'HTTP_1_1' | 'HTTP_2_PREFERRED';
+type AgentSystemContentFormat = 'STRING' | 'TEXT_PARTS';
 
 interface ModelOptions {
   agentHttpVersionPolicy: AgentHttpVersionPolicy;
+  agentSystemContentFormat: AgentSystemContentFormat;
   [key: string]: unknown;
 }
 
@@ -102,6 +104,7 @@ const formData = reactive<FormData>({
   supportToolMessage: true,
   options: {
     agentHttpVersionPolicy: 'AUTO',
+    agentSystemContentFormat: 'STRING',
   },
 });
 
@@ -111,6 +114,11 @@ const agentHttpVersionOptions = [
   { label: 'HTTP/2 优先', value: 'HTTP_2_PREFERRED' },
 ] as const;
 
+const agentSystemContentFormatOptions = [
+  { label: '字符串（默认）', value: 'STRING' },
+  { label: '内容块数组', value: 'TEXT_PARTS' },
+] as const;
+
 const normalizeAgentHttpVersionPolicy = (
   value?: unknown,
 ): AgentHttpVersionPolicy => {
@@ -120,6 +128,12 @@ const normalizeAgentHttpVersionPolicy = (
   return 'AUTO';
 };
 
+const normalizeAgentSystemContentFormat = (
+  value?: unknown,
+): AgentSystemContentFormat => {
+  return value === 'TEXT_PARTS' ? 'TEXT_PARTS' : 'STRING';
+};
+
 const normalizeModelOptions = (options?: unknown): ModelOptions => {
   const source =
     options && typeof options === 'object' && !Array.isArray(options)
@@ -130,6 +144,9 @@ const normalizeModelOptions = (options?: unknown): ModelOptions => {
     agentHttpVersionPolicy: normalizeAgentHttpVersionPolicy(
       source.agentHttpVersionPolicy,
     ),
+    agentSystemContentFormat: normalizeAgentSystemContentFormat(
+      source.agentSystemContentFormat,
+    ),
   };
 };
 
@@ -448,6 +465,19 @@ const save = async () => {
               />
             </ElSelect>
           </ElFormItem>
+          <ElFormItem v-if="!hasSpecialModelType" label="System 消息格式">
+            <ElSelect
+              v-model="formData.options.agentSystemContentFormat"
+              aria-label="System 消息格式"
+            >
+              <ElOption
+                v-for="item in agentSystemContentFormatOptions"
+                :key="item.value"
+                :label="item.label"
+                :value="item.value"
+              />
+            </ElSelect>
+          </ElFormItem>
         </div>
       </ElForm>
     </div>