fix: agree on missing files in system packs

The emulator pack recorded only loose files as a path's occupant, so a
path an archive or data tree had filled was reported missing even with
the same bytes in the ZIP, and an archive several profiles ask for was
counted once per profile. verify registered neither, and credited one
profile's file at a path holding another's. Both now record archives
and tree members in pack order; --system snk-neogeo-mvs went from 113
missing in the pack and 51 in verify to 59 on both sides.

tests/test_system_pack_parity.py

@@ -0,0 +1,65 @@
+"""A system pack and verify --system name the same missing files.
+
+The pack registered only loose files as occupants: a destination an earlier
+profile's archive or data tree had filled was reported missing even when
+the bytes were the same and in the ZIP, and an archive several profiles ask
+for was counted once per profile. verify, in turn, never registered archives
+or trees and credited a profile's file at a path holding another profile's.
+`--system snk-neogeo-mvs` said 113 missing where verify said 51.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+
+
+def _run(*argv: str) -> str:
+    result = subprocess.run(
+        [sys.executable, *argv], cwd=REPO_ROOT, capture_output=True, text=True,
+        timeout=1800,
+    )
+    if result.returncode != 0:
+        raise AssertionError(result.stdout + result.stderr)
+    return result.stdout
+
+
+class SystemPackMatchesVerify(unittest.TestCase):
+    SYSTEMS = ("snk-neogeo-mvs", "msx")
+
+    def setUp(self):
+        if not (REPO_ROOT / "database.json").exists():
+            self.skipTest("database.json is not generated")
+        self.out = Path(tempfile.mkdtemp(dir=REPO_ROOT / "tmp"))
+        self.addCleanup(shutil.rmtree, self.out, True)
+
+    def test_the_same_files_are_missing(self):
+        for system in self.SYSTEMS:
+            with self.subTest(system=system):
+                packed = _run(
+                    "scripts/generate_pack.py", "--system", system, "--offline",
+                    "--output-dir", str(self.out / system),
+                )
+                report = json.loads(_run("scripts/verify.py", "--system", system, "--json"))
+                pack_missing = sorted(re.findall(r"^  MISSING: (\S+)", packed, re.M))
+                # One per destination, as the pack reports them; an entry the
+                # collection cannot hold is counted apart on both sides.
+                verify_missing = sorted({
+                    (d["destination"], d["name"]) for d in report["details"]
+                    if d["status"] == "missing" and not d.get("unsourceable")
+                })
+                verify_missing = sorted(name for _dest, name in verify_missing)
+                self.assertTrue(pack_missing or verify_missing)
+                self.assertEqual(pack_missing, verify_missing)
+
+
+if __name__ == "__main__":
+    unittest.main()