[router] Use `get_pooled` in `process_single_choice` (#11079)

sgl-router/src/routers/grpc/router.rs

@@ -769,10 +769,13 @@ impl GrpcRouter {
 
         // Check if reasoning parsing is enabled and separate_reasoning is requested
         if original_request.separate_reasoning {
-            if let Ok(mut parser) = self
+            let pooled_parser = self
                 .reasoning_parser_factory
-                .create(&original_request.model)
-            {
+                .get_pooled(&original_request.model);
+
+            let mut parser = pooled_parser
+                .lock()
+                .map_err(|e| format!("Failed to acquire reasoning parser lock: {}", e))?;
             match parser.detect_and_parse_reasoning(&processed_text) {
                 Ok(result) => {
                     if !result.reasoning_text.is_empty() {
@@ -785,7 +788,6 @@ impl GrpcRouter {
                 }
             }
         }
-        }
 
         // Step 2: Handle tool call parsing
         let mut tool_calls: Option<Vec<crate::protocols::spec::ToolCall>> = None;