fix: count core copies under their own category

The second pass, the archive-prefix pass and the agnostic scan built
extras without source_name or source_path, so verify found no gap report
entry for them and counted game data such as hiscore.dat as core files.
Every extra now carries its entry's category and key, and verify reads
the category from the extra the builder places.

scripts/verify.py

@@ -885,7 +885,7 @@ def _mark_hidden(
     region_drops: set[str] | None = None,
     report: list[dict] | None = None,
     resolver: object | None = None,
-    placed_by: dict[str, tuple[str, str, str]] | None = None,
+    placed_kind: dict[str, str] | None = None,
 ) -> set[str]:
     """What the builder holds but cannot place beside the files it packed.
 
@@ -900,7 +900,7 @@ def _mark_hidden(
         config, emulators_dir, db,
         emu_profiles if emu_profiles is not None
         else load_emulator_profiles(emulators_dir),
-        shipped, target_cores, region_drops, placed, report, resolver, placed_by,
+        shipped, target_cores, region_drops, placed, report, resolver, placed_kind,
     )
     for u in undeclared:
         reason = hidden.get(
@@ -1333,7 +1333,7 @@ def verify_platform(
     _mark_unplaced(config, undeclared, profiles)
     from packextras import ExtraResolver
 
-    placed_by: dict[str, tuple[str, str, str]] = {}
+    placed_kind: dict[str, str] = {}
     placed = _mark_hidden(
         config, undeclared, emulators_dir, db, emu_profiles, occupied, target_cores,
         region_drops, report_for_builder,
@@ -1341,20 +1341,15 @@ def verify_platform(
             db, DEFAULT_BIOS_DIR, zip_contents, data_dir_registry, validation_index,
             validation_owners,
         ),
-        placed_by,
+        placed_kind,
     )
     # What the builder places from the cores, one per pack path, by category:
     # several entries claim one path (rom.key from three Amiga cores) and the
-    # builder ships one file there.
-    categories = {
-        (u.get("emulator", ""), u.get("name", ""), u.get("path") or ""):
-            u.get("category", "bios")
-        for u in report_for_builder
-    }
+    # builder ships one file there. The category travels on the extra: a copy
+    # the second pass makes has no gap report entry to look it up by.
     packed_extras = {"bios": 0, "game_data": 0}
-    for key in placed_by.values():
-        kind = "game_data" if categories.get(key) == "game_data" else "bios"
-        packed_extras[kind] += 1
+    for category in placed_kind.values():
+        packed_extras["game_data" if category == "game_data" else "bios"] += 1
     if not reads_file_contents(mode):
         # An existence frontend is satisfied by any file at the path, and the
         # builder fills a free platform destination with a core's file.