feat: release packs for marked platforms only

release_pack: true in the registry is the list a release builds: RetroArch,
EmuDeck, RetroBat, Batocera, RomM and MiSTer, 83% of the downloads of
v2026.10.10. generate_pack --all, --verify-packs, the pipeline consistency
step, release_record and check_release read it. Manifests are still written
for every platform.

tests/test_tool_messages.py

@@ -346,7 +346,8 @@ class ListPlatformsTakesTheSharedFlag(unittest.TestCase):
         )
         self.assertEqual(proc.returncode, 0, proc.stderr)
         lines = proc.stdout.splitlines()
-        self.assertIn("retropie (archived)", lines)
+        self.assertIn("retropie (archived, installer only)", lines)
+        self.assertIn("knulli (installer only)", lines)
         self.assertIn("retroarch", lines)