~480 scientific research skills become searchable/installable through the Skills Hub
with nothing vendored: K-Dense-AI/scientific-agent-skills (165, MIT) and
synthetic-sciences/openscience (314 across 17 category paths, Apache-2.0).
A new optional tap-level `bucket` key stamps extra["category"] on every skill from a
tap whose repo ships no skills.sh.json grouping, so several repos surface as one hub
category; a sidecar grouping still wins when present. Both repos stay at community
trust (not in TRUSTED_REPOS) so the guard scans every install.
Re-grafted from #60559 onto the post-split tools/skills_hub_github.py.
850c48cd84