[Bug]: RubyLLM::MCP::Native::Transports::StreamableHTTP#close doesn't close connections

[ebeigarts]

When closing Streamable HTTP connection and session termination fails it leaves the http connection open.

The current close method has a clear problem: if terminate_session raises (e.g., the server returns a 500), the exception propagates and neither cleanup_sse_resources nor cleanup_connection ever runs, leaving HTTP connections and SSE threads leaked.

RubyLLM::MCP::Errors::TransportError (Failed to terminate session: 500)

ruby_llm-mcp/lib/ruby_llm/mcp/native/transports/streamable_http.rb

Lines 136 to 140 in 4d10851

	def close
	terminate_session
	cleanup_sse_resources
	cleanup_connection
	end

Maybe change:

def close
  terminate_session
  cleanup_sse_resources
  cleanup_connection
end

to something like

def close
  terminate_session
ensure
  begin
    cleanup_sse_resources
  ensure
    cleanup_connection
  end
end

This guarantees:

• cleanup_sse_resources always runs — even if terminate_session raises (500, connection refused, timeout, etc.)
• cleanup_connection always runs — even if cleanup_sse_resources itself raises
• The original exception still propagates — if no subsequent exception occurs in the ensure blocks, the caller still sees the TransportError from terminate_session