feat(core): improve in-memory validation, FatturaPA detection coverage, and published type compatibility

ts/formats/validation/integrated.validator.ts

@@ -60,7 +60,8 @@ export class MainValidator {
       this.schematronEnabled = true;
       console.log(`Schematron validation enabled for ${standard} ${format}`);
     } catch (error) {
-      console.warn(`Failed to initialize Schematron: ${error.message}`);
+      const errorMessage = error instanceof Error ? error.message : String(error);
+      console.warn(`Failed to initialize Schematron: ${errorMessage}`);
     }
   }
   
@@ -121,7 +122,8 @@ export class MainValidator {
         );
         results.push(...schematronResults);
       } catch (error) {
-        console.warn(`Schematron validation error: ${error.message}`);
+        const errorMessage = error instanceof Error ? error.message : String(error);
+        console.warn(`Schematron validation error: ${errorMessage}`);
       }
     }
     
@@ -402,4 +404,4 @@ export async function createValidator(
 }
 
 // Export for convenience
-export type { ValidationReport, ValidationResult, ValidationOptions } from './validation.types.js';
+export type { ValidationReport, ValidationResult, ValidationOptions } from './validation.types.js';