Require validation preparation internally

internal/validate/standard_validator.go

@@ -34,11 +34,11 @@ type FSValidator struct {
 	root string
 }
 
-func NewStandardValidator(schemaBaseDir string) Validator {
+func NewStandardValidator(schemaBaseDir string) *StandardValidator {
 	return &StandardValidator{schemaBaseDir: schemaBaseDir}
 }
 
-func NewFSValidator(fsys fs.FS, root string) Validator {
+func NewFSValidator(fsys fs.FS, root string) *FSValidator {
 	return &FSValidator{fsys: fsys, root: root}
 }