fix: name the corrections an export withholds

scripts/export_native.py

@@ -433,7 +433,11 @@ def export_platform(
             summary += f", {refused} the format cannot state"
         if lost:
             summary += f", {lost} of theirs dropped"
+    withheld = exporter.withheld()
+    if withheld:
+        summary += f", {len(withheld)} corrections withheld"
     messages.append(summary)
+    messages.extend(f"withheld: {reason}" for reason in withheld)
     for correction in applied[:5]:
         messages.append(f"hash corrected: {correction}")
     if len(applied) > 5:

scripts/exporter/base_exporter.py

@@ -179,6 +179,14 @@ class BaseExporter(ABC):
         """
         return field_name in self.carries()
 
+    def withheld(self) -> list[str]:
+        """Corrections the render proved and still did not write, named.
+
+        Empty for most formats. One that refuses a rewrite to keep a value
+        the platform holds says so here, or the run reads as nothing to do.
+        """
+        return []
+
     def outcome(
         self,
         systems: dict[str, NativeSystem],

scripts/exporter/emudeck_exporter.py

@@ -103,6 +103,14 @@ class Exporter(BaseExporter):
             return []
         return self._md5s(systems, system_id)
 
+    def withheld(self) -> list[str]:
+        """Each check whose rewrite was refused, and the md5 that kept it."""
+        return [
+            f"{name} keeps EmuDeck's array: rewriting it would drop "
+            f"{', '.join(sorted(values))}, which no profile carries"
+            for name, values in sorted(getattr(self, "_withdrawn", {}).items())
+        ]
+
     def _refused_systems(self) -> set[str]:
         withdrawn = getattr(self, "_withdrawn", {})
         return {FUNCTION_HASH_MAP[name] for name in withdrawn if name in FUNCTION_HASH_MAP}