ax(node): rename channel to responseChannel in handleResponse

AX Principle 1 — predictable names over short names. The variable
`channel` in handleResponse required context to understand its role;
`responseChannel` is self-describing on first read.

Co-Authored-By: Charon <charon@lethean.io>

pkg/node/controller.go

@@ -45,15 +45,15 @@ func (ctrl *Controller) handleResponse(conn *PeerConnection, msg *Message) {
 	}
 
 	ctrl.mutex.Lock()
-	channel, exists := ctrl.pendingRequests[msg.ReplyTo]
+	responseChannel, exists := ctrl.pendingRequests[msg.ReplyTo]
 	if exists {
 		delete(ctrl.pendingRequests, msg.ReplyTo)
 	}
 	ctrl.mutex.Unlock()
 
-	if exists && channel != nil {
+	if exists && responseChannel != nil {
 		select {
-		case channel <- msg:
+		case responseChannel <- msg:
 		default:
 			// Channel full or closed
 		}