Convert to multisets, facts as actions, and update multiset example

[saulshanabrook]

No description provided.

[codspeed-hq]

CodSpeed Performance Report

Merging #382 will not alter performance

_{Comparing demo (e6ad4fa) with main (6daa0ae)¹}

Summary

✅ 14 untouched

Footnotes

1. No successful run was found on main (e6ad4fa) during the generation of this report, so 6daa0ae was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩