add staticcheck linter

.golangci.yml

@@ -6,7 +6,7 @@ run:
   go: '1.24'
 
 linters:
-  disable: [dupl, errcheck, goconst, godot, staticcheck, predeclared]
+  disable: [dupl, errcheck, goconst, godot]
   enable:
     # Default enabled linters
     - errcheck # Check for unchecked errors

cmd/x32-cli/matrix.go

@@ -22,7 +22,7 @@ type MatrixCmdGroup struct {
 
 func (cmd *MatrixCmdGroup) Validate() error {
 	if cmd.Index.Index < 1 || cmd.Index.Index > 6 {
-		return fmt.Errorf("Matrix output index must be between 1 and 6, got %d", cmd.Index.Index)
+		return fmt.Errorf("matrix output index must be between 1 and 6, got %d", cmd.Index.Index)
 	}
 	return nil
 }