ax(mining): rename msg to clientMessage in wsClient.readPump

AX Principle 1 — predictable names over short names. `msg` required
reading the struct to understand what it contained; `clientMessage`
is self-describing at the call site.

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

pkg/mining/events.go

@@ -348,24 +348,24 @@ func (client *wsClient) readPump() {
 		}
 
 		// Parse client message
-		var msg struct {
+		var clientMessage struct {
 			Type   string   `json:"type"`
 			Miners []string `json:"miners,omitempty"`
 		}
-		if err := UnmarshalJSON(message, &msg); err != nil {
+		if err := UnmarshalJSON(message, &clientMessage); err != nil {
 			continue
 		}
 
-		switch msg.Type {
+		switch clientMessage.Type {
 		case "subscribe":
 			// Update miner subscription (protected by mutex)
 			client.minersMutex.Lock()
 			client.miners = make(map[string]bool)
-			for _, m := range msg.Miners {
+			for _, m := range clientMessage.Miners {
 				client.miners[m] = true
 			}
 			client.minersMutex.Unlock()
-			logging.Debug("client subscribed to miners", logging.Fields{"miners": msg.Miners})
+			logging.Debug("client subscribed to miners", logging.Fields{"miners": clientMessage.Miners})
 
 		case "ping":
 			// Respond with pong