fix: finalize only the packs this run names

scripts/generate_pack.py

@@ -3480,12 +3480,15 @@ def verify_and_finalize_packs(
     all_ok = True
 
     # Map ZIP names to platform names
+    # By the exact name this run's reduction gives a platform's pack, never by
+    # substring: a _Custom or regional pack left by another run was judged
+    # against this run's expectation and failed it.
+    registered = list_registered_platforms(platforms_dir, include_archived=True)
+    expected = _expected_pack_names(registered, platforms_dir, regions, target_name)
     pack_to_platform: dict[str, list[str]] = {}
     for name in _pack_archives(output_dir):
-        for pname in list_registered_platforms(platforms_dir, include_archived=True):
-            cfg = load_platform_config(pname, platforms_dir)
-            display = cfg.get("platform", pname).replace(" ", "_")
-            if display in name or display.replace("_", "") in name.replace("_", ""):
+        for pname in registered:
+            if name in expected[pname]:
                 pack_to_platform.setdefault(name, []).append(pname)
 
     for name in _pack_archives(output_dir):

tests/test_finalize_pack_names.py

@@ -0,0 +1,36 @@
+"""The post-build check judges only the packs this run would name.
+
+A MiSTer _Custom pack left in the directory by a --from-md5 run was
+attached to misterfpga by substring and checked against the full list:
+0/81, FAILED, exit code 1, for a run whose own pack was 81/81.
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+import tempfile
+import unittest
+import zipfile
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+
+class FinalizeByExactName(unittest.TestCase):
+    def test_a_custom_pack_is_not_judged_as_the_platform_pack(self):
+        from generate_pack import verify_and_finalize_packs
+
+        previous = os.getcwd()
+        os.chdir(REPO_ROOT)
+        self.addCleanup(os.chdir, previous)
+        with tempfile.TemporaryDirectory(dir=REPO_ROOT / "tmp") as tmp:
+            with zipfile.ZipFile(Path(tmp) / "MiSTer_FPGA_Custom_BIOS_Pack.zip", "w") as zf:
+                zf.writestr("README.txt", "custom")
+            ok = verify_and_finalize_packs(tmp, {"files": {}, "indexes": {}})
+        self.assertTrue(ok)
+
+
+if __name__ == "__main__":
+    unittest.main()