fix: compare pack paths, not only counts

Step 5 compared (ok, total) and the core file count. RetroArch, Lakka
and RetroPie read 526/526 on both sides while verify credited four paths
below SGB1.sfc and SGB2.sfc that the pack never writes: a declared file
blocks them as a directory. verify now places the platform files in the
builder's order with the same path rules, and a user_provided or
external declaration keeps its slot on both sides, so no core file takes
it in the report only.

verify --destinations writes the paths each pack holds by the report,
and step 5 compares them with the archive members (notes and data tree
members set aside). Every emulator profile, in each build it has, is
built in memory (PackRecord, nothing read or written) and compared with
verify --emulator path by path. Cost measured here: about 1 s per
platform archive and 11 s for the 930 emulator packs.

scripts/packextras.py

@@ -209,7 +209,7 @@ def hidden_extras(
     emulators_dir: str,
     db: dict,
     profiles: dict,
-    shipped: dict[str, str],
+    shipped: dict[str, str | None],
     target_cores: set[str] | None = None,
     region_drops: set[str] | None = None,
     placed: set[str] | None = None,
@@ -229,7 +229,8 @@ def hidden_extras(
     while the report counted it in the pack. A twin carrying the same bytes
     serves the core on the filesystem that folds the names, so it is not a
     file left out. ``shipped`` maps the full destination of each platform
-    file the pack carries to its local copy. ``placed``, when given,
+    file the pack carries to its local copy, or to None for a slot it keeps
+    without one (user_provided, external). ``placed``, when given,
     receives the full destination of each held extra the pack carries.
     ``resolver`` is the builder's lookup. An extra it cannot resolve is
     skipped and takes no path, as the builder skips it.