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

ts_install/download-test-samples.ts

@@ -1,4 +1,5 @@
 #!/usr/bin/env node
+/// <reference types="node" />
 
 /**
  * Download official EN16931 and PEPPOL test samples for conformance testing
@@ -142,7 +143,8 @@ async function downloadTestSamples(source: TestSampleSource): Promise<void> {
     try {
       await downloadFile(source.repository, source.branch, filePath, targetPath);
     } catch (error) {
-      console.error(`  ❌ Error downloading ${fileName}: ${error.message}`);
+      const errorMessage = error instanceof Error ? error.message : String(error);
+      console.error(`  ❌ Error downloading ${fileName}: ${errorMessage}`);
     }
   }
 }
@@ -203,4 +205,4 @@ if (import.meta.url === `file://${process.argv[1]}`) {
 }
 
 export default main;
-export { TEST_SAMPLE_SOURCES };
+export { TEST_SAMPLE_SOURCES };