BREAKING CHANGE(core): Refactor contact and PDF handling across the library by replacing IContact with TContact and updating PDF processing to use a structured IPdf object. These changes ensure that empty contact objects include registration details, founded/closed dates, and status, and that PDF loading/exporting uniformly wraps buffers in a proper object.

ts/formats/xinvoice.decoder.ts

@@ -118,21 +118,37 @@ export class XInvoiceDecoder extends BaseDecoder {
                         'Unknown Buyer';
                         
       // Create seller contact
-      const seller: plugins.tsclass.business.IContact = {
+      const seller: plugins.tsclass.business.TContact = {
         name: sellerName,
         type: 'company',
         description: sellerName,
         address: {
           streetName: sellerStreet,
-          houseNumber: '0',  // Required by IAddress interface
+          houseNumber: '0',
           city: sellerCity,
           country: sellerCountry,
           postalCode: sellerPostcode,
         },
+        registrationDetails: {
+          vatId: this.getElementText('cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme/cbc:CompanyID') || 'Unknown',
+          registrationId: this.getElementText('cac:AccountingSupplierParty/cac:Party/cac:PartyLegalEntity/cbc:CompanyID') || 'Unknown',
+          registrationName: sellerName
+        },
+        foundedDate: {
+          year: 2000,
+          month: 1,
+          day: 1
+        },
+        closedDate: {
+          year: 9999,
+          month: 12,
+          day: 31
+        },
+        status: 'active'
       };
       
       // Create buyer contact
-      const buyer: plugins.tsclass.business.IContact = {
+      const buyer: plugins.tsclass.business.TContact = {
         name: buyerName,
         type: 'company',
         description: buyerName,
@@ -143,6 +159,22 @@ export class XInvoiceDecoder extends BaseDecoder {
           country: 'Unknown',
           postalCode: 'Unknown',
         },
+        registrationDetails: {
+          vatId: this.getElementText('cac:AccountingCustomerParty/cac:Party/cac:PartyTaxScheme/cbc:CompanyID') || 'Unknown',
+          registrationId: this.getElementText('cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cbc:CompanyID') || 'Unknown',
+          registrationName: buyerName
+        },
+        foundedDate: {
+          year: 2000,
+          month: 1,
+          day: 1
+        },
+        closedDate: {
+          year: 9999,
+          month: 12,
+          day: 31
+        },
+        status: 'active'
       };
       
       // Extract invoice type