fix: end --verify-packs on a summary line

The check ended on the last platform's line: a failing pack was named only above its own errors. It now names every failing pack on stderr at the end, as the build path does, or counts the packs found OK.

scripts/generate_pack.py

@@ -2588,6 +2588,7 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
     )
 
     verified = 0
+    failing: list[str] = []
     for platform_name in platforms:
         found = sorted(expected[platform_name] & on_disk)
         verified += len(found)
@@ -2601,6 +2602,7 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
                     f"generate_pack.py --platform {platform_name} --output-dir {args.output_dir})"
                 )
                 all_ok = False
+                failing.append(f"{platform_name} (no pack)")
             else:
                 print(f"  {platform_name}: SKIP (no pack in {args.output_dir})")
             continue
@@ -2646,7 +2648,17 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
                 for err in errors:
                     print(f"    {err}")
                 all_ok = False
+                failing.append(f"{platform_name} ({pack_name})")
 
+    if failing:
+        # Named at the end, where the log is read, and on stderr, as the
+        # build path does: a failing pack sat among its own error lines.
+        print(
+            f"ERROR: packs failed verification: {', '.join(failing)}",
+            file=sys.stderr,
+        )
+    elif verified:
+        print(f"Verified {verified} pack{'s' if verified != 1 else ''}: all OK")
     if not verified:
         # Every platform skipped is no check at all: a mistyped or purged
         # output directory read as a passed integrity check.