The neon CI image ships neither the Plasma QML modules nor kpackagetool6,
so the appstream-metainfo step failed with command-not-found. Guard it:
run it when kpackagetool6 exists (local desktop, still fails on real
errors), skip with a notice otherwise.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>