修复流式参数处理：尊重客户端明确指定的stream参数

- 修正transformers中强制添加stream=true的错误逻辑
- 只有客户端明确指定stream参数时才转发该参数
- 客户端未指定stream时不强制添加，保持原有意图
- 更新routes.js中相应的流式判断逻辑
- 确保非流式请求得到正确处理

transformers/request-anthropic.js

@@ -6,10 +6,14 @@ export function transformToAnthropic(openaiRequest) {
   
   const anthropicRequest = {
     model: openaiRequest.model,
-    messages: [],
-    stream: openaiRequest.stream !== false
+    messages: []
   };
 
+  // Only add stream parameter if explicitly provided by client
+  if (openaiRequest.stream !== undefined) {
+    anthropicRequest.stream = openaiRequest.stream;
+  }
+
   // Handle max_tokens
   if (openaiRequest.max_tokens) {
     anthropicRequest.max_tokens = openaiRequest.max_tokens;

transformers/request-openai.js

@@ -7,10 +7,14 @@ export function transformToOpenAI(openaiRequest) {
   const targetRequest = {
     model: openaiRequest.model,
     input: [],
-    store: false,
-    stream: openaiRequest.stream !== false
+    store: false
   };
 
+  // Only add stream parameter if explicitly provided by client
+  if (openaiRequest.stream !== undefined) {
+    targetRequest.stream = openaiRequest.stream;
+  }
+
   // Transform max_tokens to max_output_tokens
   if (openaiRequest.max_tokens) {
     targetRequest.max_output_tokens = openaiRequest.max_tokens;