mapping-commons/sssom-py: v0.4.19 release

What's Changed

• Apply black 2026 styling by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/642
• Allow unicode on YAML dump by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/641
• Bump minimum LinkML pin to v1.10 by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/646
• Update SSSOM Extended Prefix Map by @github-actions[bot] in https://github.com/mapping-commons/sssom-py/pull/631
• Migrate documentation system to mkdocs by @matentzn in https://github.com/mapping-commons/sssom-py/pull/647
• Handle multi-valued slots that are None when serializing to RDF by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/636
• Make more explicit columns in basic TSV reading test by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/596
• Remove redundant axis= parameter to df.drop(). by @gouttegd in https://github.com/mapping-commons/sssom-py/pull/649
• Only run rdflib-endpoint test if software is available by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/650
• Replace poetry with uv by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/651
• Bump sssom-schema to 1.1.0a4 by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/653
• Add maintainers list to pyproject.toml by @cthoyt in https://github.com/mapping-commons/sssom-py/pull/654

Full Changelog: https://github.com/mapping-commons/sssom-py/compare/v0.4.18...v0.4.19