fix: keep RomM files where its player reads them

RomM lists a platform's firmware folder without descending (base_handler.py:1002, recursive=False) and EmulatorJS writes the chosen file, or each zip member, under its bare name. 543 files of the RomM pack sat below a folder where no core could read them. The registry now marks RomM's folder flat, and such files are omitted with the reason below_platform_folder in the manifest and the installer.

scripts/generate_pack.py

@@ -3859,7 +3859,7 @@ def _record_unplaceable(unplaceable: list[dict], record_omission: Callable[...,
     for u in unplaceable:
         record_omission(
             u.get("path") or u.get("name", ""), u, u.get("system") or "",
-            "no_platform_slug", [u.get("emulator", "")],
+            u.get("unplaceable", "no_platform_slug"), [u.get("emulator", "")],
         )