fix(pdfa): preserve compliance via incremental update on compression

- Change PdfWriter to use incremental=True to preserve XMP/OutputIntents

- Add inflation protection fallback in engine.compress_pdfa

core/engine.py

@@ -58,8 +58,11 @@ class PDFEngine:
 
     @staticmethod
     def compress_pdfa(data: bytes, quality: int = 60) -> bytes:
-        """Comprime mantendo a estrutura PDF/A."""
-        return compress_pdfa(data, quality=quality)
+        """Comprime mantendo a estrutura PDF/A (protegido contra inflação)."""
+        result = compress_pdfa(data, quality=quality)
+        if len(result) >= len(data):
+            return data
+        return result
 
     @staticmethod
     def detect_pdfa(data: bytes) -> dict: