refactor: Move downloaded resources from assets/ to assets_downloaded/

- Changed default download location to assets_downloaded/schematron
- Updated all references in SchematronDownloader, integration, and validator
- Updated postinstall scripts to use new location
- assets_downloaded/ is already in .gitignore to exclude downloaded files from git
- Moved existing downloaded files to new location
- All functionality tested and working correctly

ts_install/download-schematron.ts

@@ -9,7 +9,7 @@ import { SchematronDownloader } from '../dist_ts/formats/validation/schematron.d
 async function main() {
   console.log('📥 Starting Schematron download...\n');
   
-  const downloader = new SchematronDownloader('assets/schematron');
+  const downloader = new SchematronDownloader('assets_downloaded/schematron');
   await downloader.initialize();
   
   // Download EN16931 Schematron files

ts_install/index.ts

@@ -49,7 +49,7 @@ function getFileChecksum(filePath: string): string | null {
  * Check if resources are already downloaded and valid
  */
 function checkExistingResources(): boolean {
-  const versionFile = path.join('assets', 'schematron', '.version');
+  const versionFile = path.join('assets_downloaded', 'schematron', '.version');
   
   try {
     if (!fs.existsSync(versionFile)) return false;
@@ -62,9 +62,9 @@ function checkExistingResources(): boolean {
     
     // Check if key files exist
     const keyFiles = [
-      'assets/schematron/EN16931-UBL-v1.3.14.sch',
-      'assets/schematron/EN16931-CII-v1.3.14.sch',
-      'assets/schematron/PEPPOL-EN16931-UBL-v3.0.17.sch'
+      'assets_downloaded/schematron/EN16931-UBL-v1.3.14.sch',
+      'assets_downloaded/schematron/EN16931-CII-v1.3.14.sch',
+      'assets_downloaded/schematron/PEPPOL-EN16931-UBL-v3.0.17.sch'
     ];
     
     for (const file of keyFiles) {
@@ -84,7 +84,7 @@ function checkExistingResources(): boolean {
  * Save version file after successful download
  */
 function saveVersionFile(): void {
-  const versionFile = path.join('assets', 'schematron', '.version');
+  const versionFile = path.join('assets_downloaded', 'schematron', '.version');
   try {
     fs.mkdirSync(path.dirname(versionFile), { recursive: true });
     fs.writeFileSync(versionFile, RESOURCES_VERSION);
@@ -96,7 +96,7 @@ function saveVersionFile(): void {
 async function downloadSchematron() {
   console.log('📥 Downloading Schematron validation files...\n');
   
-  const downloader = new SchematronDownloader('assets/schematron');
+  const downloader = new SchematronDownloader('assets_downloaded/schematron');
   await downloader.initialize();
   
   let successCount = 0;