fix: group core files under their pack path

On a platform that writes bios/ in front of its destinations (RetroDECK, AmberELEC, EmuELEC), a core extra was grouped, dropped and held under its bare destination while the platform's declaration of the same file used bios/<name>. Beetle PSX's scph5501.bin was kept by the --region japan pack while the declaration was dropped and the installer dropped the path. extra_region_key keys every extra with the platform's declared root, in the builder, the manifest selection, verify's replay and the omissions. The same key gives the declared entries the systems of the core files at their path: every --system case of RetroDECK differed between pack and installer before, none does now.

scripts/manifestselect.py

@@ -19,7 +19,13 @@ from dataclasses import dataclass
 
 import region as region_mod
 from common import _norm_system_id, sanitize_pack_path
-from packextras import _kept, _serving_system_ids, extra_region_groups, system_spellings
+from packextras import (
+    _kept,
+    _serving_system_ids,
+    extra_region_groups,
+    extra_region_key,
+    system_spellings,
+)
 
 
 def _dest(entry: dict) -> str:
@@ -44,6 +50,7 @@ class SelectionIndex:
         pack_systems: dict[str, dict],
         extras: list[dict],
         required_only: bool = False,
+        extras_prefix: str = "",
     ) -> SelectionIndex:
         by_norm: dict[str, set[str]] = {}
         for sys_id in pack_systems:
@@ -60,7 +67,8 @@ class SelectionIndex:
         extra_groups: dict[str, set[str]] = {}
         spellings = system_spellings(pack_systems)
         for extra in extras:
-            dest = _dest(extra)
+            # Keyed as platform_region_groups keys it (extra_region_key).
+            dest = extra_region_key(extra, extras_prefix)
             if not dest:
                 continue
             extra_groups.setdefault(dest, set()).update(