fix: count a recalbox element kept as written

An element whose md5 the truth contradicts without naming another is
written back whole. It was counted as an entry the format cannot keep.
It now counts as kept, and the md5 it keeps is named as withheld.

scripts/exporter/recalbox_exporter.py

@@ -222,6 +222,19 @@ class Exporter(BaseExporter):
             return False
         return super().states(fe, field_name)
 
+    def lands(self, fe: NativeFile) -> bool:
+        """An element of theirs the render cannot rewrite is still in the
+        file, written back as Recalbox wrote it."""
+        return self.writable(fe) or id(fe) in getattr(self, "_held_whole", {})
+
+    def withheld(self) -> list[str]:
+        """Each element kept as written because the truth names no md5."""
+        return [
+            f"{label} keeps its md5: the truth accepts another dump and "
+            "names no md5 for it, which es_bios.xsd requires"
+            for label in sorted(getattr(self, "_held_whole", {}).values())
+        ]
+
     @classmethod
     def writable(cls, fe: NativeFile, require: str = "") -> bool:
         """es_bios.xsd makes md5 and core required: without them, no element.
@@ -272,6 +285,21 @@ class Exporter(BaseExporter):
                     for s in root.iter("system")
                 ]
 
+        # Elements of theirs written back as they stand, by (platform, path).
+        held = {
+            (platform, " ".join(child.get("path", "").split()))
+            for platform, _, children in theirs
+            for child in children
+            if isinstance(child, dict)
+        }
+        self._held_whole = {
+            id(fe): f"{system.native_id}/{self._path(fe)}"
+            for system in systems.values()
+            for fe in system.files
+            if fe.platform is not None
+            and not self.writable(fe)
+            and (system.native_id, " ".join(self._path(fe).split())) in held
+        }
         ours: dict[str, tuple[NativeSystem, dict[str, tuple[NativeFile, str]]]] = {}
         for system in systems.values():
             writable = [fe for fe in system.files if self.writable(fe)]