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

ts/formats/validation/conformance.harness.ts

@@ -185,7 +185,8 @@ export class ConformanceTestHarness {
           r.source === 'Schematron'
         );
       } catch (error) {
-        console.warn(`Schematron not available for ${sample.format}: ${error.message}`);
+        const errorMessage = error instanceof Error ? error.message : String(error);
+        console.warn(`Schematron not available for ${sample.format}: ${errorMessage}`);
       }
       
       // Aggregate results
@@ -202,12 +203,13 @@ export class ConformanceTestHarness {
       result.passed = result.errors.length === 0 === sample.expectedValid;
       
     } catch (error) {
-      console.error(`Error testing ${sample.name}: ${error.message}`);
+      const errorMessage = error instanceof Error ? error.message : String(error);
+      console.error(`Error testing ${sample.name}: ${errorMessage}`);
       result.errors.push({
         ruleId: 'TEST-ERROR',
         source: 'TestHarness',
         severity: 'error',
-        message: `Test execution failed: ${error.message}`
+        message: `Test execution failed: ${errorMessage}`
       });
     }
     
@@ -588,4 +590,4 @@ export async function runConformanceTests(
     // Generate HTML report
     await harness.generateHTMLReport();
   }
-}
+}