HttpClientStreamableHttpTransport: handle HTTP 405

- Fixes #877

Signed-off-by: Daniel Garnier-Moiroux <git@garnier.wf>

Author: Kehrlann

mcp-core/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java

@@ -298,6 +298,10 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
 											"Authorization error connecting to SSE stream",
 											responseEvent.responseInfo()));
 						}
+						if (statusCode == METHOD_NOT_ALLOWED) {
+							logger.debug("The server does not support SSE streams, using request-response mode.");
+							return Flux.empty();
+						}
 
 						if (!(responseEvent instanceof ResponseSubscribers.SseResponseEvent sseResponseEvent)) {
 							return Flux.<McpSchema.JSONRPCMessage>error(new McpTransportException(
@@ -344,10 +348,6 @@ else if (statusCode >= 200 && statusCode < 300) {
 								return Flux.empty();
 							}
 						}
-						else if (statusCode == METHOD_NOT_ALLOWED) { // NotAllowed
-							logger.debug("The server does not support SSE streams, using request-response mode.");
-							return Flux.empty();
-						}
 						else if (statusCode == NOT_FOUND) {
 
 							if (transportSession != null && transportSession.sessionId().isPresent()) {