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

ts/formats/base/base.decoder.ts

@@ -37,6 +37,13 @@ export abstract class BaseDecoder {
     return this.xml;
   }
 
+  /**
+   * Gets a parsed XML document when a decoder keeps one around.
+   */
+  public getParsedDocument(): Document | undefined {
+    return undefined;
+  }
+
   /**
    * Parses a CII date string based on format code
    * @param dateStr Date string