fix(lint): resolve errcheck and unparam violations

Fixes CI lint failures by handling unchecked error returns and marking
unused parameters with blank identifiers.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/down.go

@@ -95,7 +95,7 @@ func runDown(cmd *cobra.Command, args []string) error {
 		if err != nil {
 			return fmt.Errorf("cannot proceed: %w", err)
 		}
-		defer lock.Unlock()
+		defer func() { _ = lock.Unlock() }()
 	}
 	allOK := true