ax(mining): replace prose doc comment with usage example on XMRigMiner.Stop

AX Principle 2: comments show HOW with real values, not what the signature already says.

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

pkg/mining/xmrig_start.go

@@ -150,7 +150,8 @@ func (m *XMRigMiner) Start(config *Config) error {
 	return nil
 }
 
-// Stop terminates the miner process and cleans up the instance-specific config file.
+// miner.Stop()
+// if err := miner.Stop(); err != nil { log.Printf("stop failed: %v", err) }
 func (m *XMRigMiner) Stop() error {
 	// Call the base Stop to kill the process
 	if err := m.BaseMiner.Stop(); err != nil {