BREAKING CHANGE(core): Rebrand XInvoice to EInvoice: update package name, class names, imports, and documentation

test/test.corpus-master.ts

@@ -13,7 +13,7 @@ tap.test('Run all corpus tests', async () => {
   // Generate a summary report from existing results
   try {
     // Create a simple summary
-    const summary = `# XInvoice Corpus Testing Summary
+    const summary = `# EInvoice Corpus Testing Summary
 
 Generated on: ${new Date().toISOString()}