Suppress debug logs for model routing and ignore empty tools arrays

- Comment out verbose routing logs in the API server to reduce noise.
- Remove the `tools` field from Qwen client requests when it is an empty array.
- Add guards in Claude, Codex, Gemini‑CLI, and Gemini translators to skip tool conversion when the `tools` array is empty, preventing unnecessary payload modifications.

internal/api/server.go

@@ -140,10 +140,10 @@ func (s *Server) unifiedModelsHandler(openaiHandler *openai.OpenAIAPIHandler, cl
 
 		// Route to Claude handler if User-Agent starts with "claude-cli"
 		if strings.HasPrefix(userAgent, "claude-cli") {
-			log.Debugf("Routing /v1/models to Claude handler for User-Agent: %s", userAgent)
+			// log.Debugf("Routing /v1/models to Claude handler for User-Agent: %s", userAgent)
 			claudeHandler.ClaudeModels(c)
 		} else {
-			log.Debugf("Routing /v1/models to OpenAI handler for User-Agent: %s", userAgent)
+			// log.Debugf("Routing /v1/models to OpenAI handler for User-Agent: %s", userAgent)
 			openaiHandler.OpenAIModels(c)
 		}
 	}