fix: Optimize SSE Transport Configuration

1. **Duplicate SSE Connections Problem**
   - When both WebFlux and HTTP Client are available, `McpClientAutoConfiguration` loads both implementations
   - `SseWebFluxTransportAutoConfiguration` and `SseHttpClientTransportAutoConfiguration` create duplicate connections
   - Results in unnecessary resource consumption and potential performance issues

2. **Duplicate MCP Tools Creation**
   - Multiple identical MCP tools are created due to duplicate transport implementations
   - Affects system efficiency and resource utilization
   - May cause confusion in tool management and callbacks

1. **Transport Mode Configuration**
   ```java
   public enum SseTransportMode {
       WEBFLUX,    // Default implementation
       HTTP_CLIENT
   }
   ```

2. **Configuration Property**
   ```properties
   spring.ai.mcp.client.sse.transport-mode=WEBFLUX  # Default
   # or
   spring.ai.mcp.client.sse.transport-mode=HTTP_CLIENT
   ```

3. **Implementation Details**
   - Add transport mode selection in `McpSseClientProperties`
   - Use conditional loading to ensure single implementation
   - Optimize tool creation process
   - Maintain backward compatibility

1. Resource Efficiency
   - Single SSE connection per endpoint
   - Optimized tool initialization
   - Reduced memory footprint

2. Better Configuration Control
   - Explicit transport mode selection
   - Clear configuration options
   - IDE support with metadata

3. Improved Stability
   - Prevents duplicate connections
   - Streamlined tool management
   - Better error handling

1. Verify single transport initialization
2. Test tool creation and management
3. Validate configuration switching
4. Check backward compatibility

- `McpClientAutoConfiguration.java`
- `McpSseClientProperties.java`
- `SseWebFluxTransportAutoConfiguration.java`
- `SseHttpClientTransportAutoConfiguration.java`

Labels: enhancement, optimization, configuration

Author: aliyun1024qjc