fix: settle export sizes, never write None

A truth that accepts several sizes left an export with no size even
where the platform states one of them for the same dump, and RomM's
fixture then received the string None, which RomM cannot parse. A
size list now admits the platform's own size, RomM keeps its value
when nothing settles one, and validation requires a number.

scripts/exporter/baseline.py

@@ -188,9 +188,21 @@ class NativeFile:
             "platform": (self.platform, self.truth),
             "truth": (self.truth,),
         }.get(source, (self.truth, self.platform))
+        # A list names every size the code accepts (geargrafx's syscard3.pce,
+        # headerless or headered). It states no single size, but it still
+        # admits the one the platform writes: System.dat's 262144 for the
+        # same md5 lost its size field when the list came first.
+        accepted: set[int] | None = None
         for entry in order:
-            if entry and entry.get("size"):
-                return _single_size(entry["size"])
+            if not entry or not entry.get("size"):
+                continue
+            single = _single_size(entry["size"])
+            if single is None:
+                if accepted is None:
+                    accepted = {int(v) for v in entry["size"]}
+                continue
+            if accepted is None or single in accepted:
+                return single
         return None
 
     def native(self, key: str, default: object = "") -> object:

scripts/exporter/romm_exporter.py

@@ -127,7 +127,13 @@ class Exporter(BaseExporter):
                     continue
                 entry: OrderedDict[str, str] = OrderedDict()
                 # The fixture states every value as a string, size included.
-                entry["size"] = str(fe.size())
+                # Where the model settles no size, RomM's own value stands;
+                # str(None) wrote "None", and RomM's int() on it raised.
+                size = fe.size()
+                if size is None and fe.platform is not None:
+                    size = fe.platform.get("size")
+                if size is not None:
+                    entry["size"] = str(int(size))
                 crc = fe.record_hash("crc32")
                 if crc:
                     entry["crc"] = crc
@@ -159,7 +165,7 @@ class Exporter(BaseExporter):
                 issues.append(f"key without a platform slug: {key}")
             elif not self._known_platform(slug):
                 issues.append(f"platform slug RomM does not know: {slug}")
-            if not entry.get("size"):
+            if not str(entry.get("size", "")).isdigit():
                 issues.append(f"entry without a size, never verifiable: {key}")
             if not any(entry.get(h) for h in ("md5", "sha1", "crc")):
                 issues.append(f"entry without a hash, never verifiable: {key}")