feat: gate claw runtime selection by availability

scripts/install-local-launchagent.sh

@@ -25,6 +25,7 @@ config_path = sys.argv[2]
 text = plist_path.read_text()
 plist_path.write_text(text.replace("__BOSS_AGENT_CONFIG__", config_path))
 PY
+plutil -lint "$PLIST_TARGET" >/dev/null
 launchctl unload "$PLIST_TARGET" >/dev/null 2>&1 || true
 launchctl load "$PLIST_TARGET"
 echo "Loaded $PLIST_TARGET with $CONFIG_PATH"