support 405 response from servers that don’t support streaming (#90)

* support 405 response from servers that don’t support streaming

* Rephrase comment

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Co-authored-by: Stephen Tallent <stallent@mercury.io>
Co-authored-by: Mattt Zmuda <mattt@loopwork.com>

Author: 3 people

Sources/MCP/Base/Transports/HTTPClientTransport.swift

@@ -205,6 +205,12 @@ public actor HTTPClientTransport: Actor, Transport {
 
             // Check response status
             guard httpResponse.statusCode == 200 else {
+                // If the server returns 405 Method Not Allowed,
+                // it indicates that the server doesn't support SSE streaming.
+                // We should cancel the task instead of retrying the connection.
+                if httpResponse.statusCode == 405 {
+                    self.streamingTask?.cancel()
+                }
                 throw MCPError.internalError("HTTP error: \(httpResponse.statusCode)")
             }