feat: add informative logging to synchronous tool execution

Improvements to synchronous executeToolCalls() method:

1. Enhanced execution log:
   - Changed: 'Executing tool call: {}'
   - To: 'Executing tool call: {} (synchronous mode)'
   - Purpose: Clearly indicate the execution mode

2. Added performance awareness log:
   - When an AsyncToolCallback is executed synchronously
   - Log message suggests using executeToolCallsAsync() for better performance
   - Helps users identify optimization opportunities

Benefits:
✅ Users can easily distinguish sync vs async execution
✅ Performance optimization opportunities are visible
✅ Consistent logging between sync and async methods
✅ Helps with debugging and performance tuning

Example logs:
  DEBUG - Executing tool call: weatherTool (synchronous mode)
  DEBUG - Tool 'weatherTool' implements AsyncToolCallback but executing
          in synchronous mode. Consider using executeToolCallsAsync()
          for better performance.

All 18 tests in DefaultToolCallingManagerTests passed.

Related: #async-tool-support
Signed-off-by: shaojie <741047428@qq.com>

Author: JGoP-L

spring-ai-model/src/main/java/org/springframework/ai/model/tool/DefaultToolCallingManager.java

@@ -226,9 +226,9 @@ private InternalToolExecutionResult executeToolCall(Prompt prompt, AssistantMess
 
 		for (AssistantMessage.ToolCall toolCall : assistantMessage.getToolCalls()) {
 
-			logger.debug("Executing tool call: {}", toolCall.name());
-
 			String toolName = toolCall.name();
+
+			logger.debug("Executing tool call: {} (synchronous mode)", toolName);
 			String toolInputArguments = toolCall.arguments();
 
 			// Handle the possible null parameter situation in streaming mode.
@@ -252,6 +252,12 @@ private InternalToolExecutionResult executeToolCall(Prompt prompt, AssistantMess
 				throw new IllegalStateException("No ToolCallback found for tool name: " + toolName);
 			}
 
+			// Log tool type information for performance awareness
+			if (toolCallback instanceof AsyncToolCallback) {
+				logger.debug("Tool '{}' implements AsyncToolCallback but executing in synchronous mode. "
+						+ "Consider using executeToolCallsAsync() for better performance.", toolName);
+			}
+
 			if (returnDirect == null) {
 				returnDirect = toolCallback.getToolMetadata().returnDirect();
 			}