fix: file a slug-platform bios under its own system

scripts/common.py

@@ -1593,6 +1593,11 @@ SYSTEM_ALIASES: dict[str, str] = {
     "sega32x": "sega-32x",
     "segastv": "sega-stv",
     "ti994a": "ti99",
+    # Other spellings of one machine: RomM files the Mega CD as sega-mega-cd
+    # and the disk system as nintendo-fds, which normalize to the ids the
+    # profiles use only through these.
+    "sega-segacd": "sega-megacd",
+    "nes-fds": "nintendo-fds",
 }
 
 

scripts/packextras.py

@@ -120,7 +120,19 @@ def _map_emulator_to_slug(
 def _slug_for(
     u: dict, profiles: dict, platform_systems: set, norm_map: dict, sys_to_slug: dict
 ) -> str:
-    """The platform slug a report entry's emulator files under, or empty."""
+    """The platform slug a report entry files under, or empty.
+
+    The entry's own system decides first: picodrive's Mega CD BIOS belongs
+    under segacd/, where RomM looks for a Mega CD game's firmware, not under
+    gamegear/, the first of the emulator's systems.
+    """
+    own = u.get("system")
+    if own:
+        slug = _map_emulator_to_slug(
+            {"systems": [own]}, platform_systems, norm_map, sys_to_slug
+        )
+        if slug:
+            return slug
     emu_name = u.get("profile") or u.get("emulator", "")
     profile = profiles.get(emu_name, {})
     if not profile: