Bump furo from 2025.9.25 to 2025.12.19

Bumps [furo](https://github.com/pradyunsg/furo) from 2025.9.25 to 2025.12.19.
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2025.09.25...2025.12.19)

---
updated-dependencies:
- dependency-name: furo
  dependency-version: 2025.12.19
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -44,7 +44,7 @@ optional-dependencies.dev = [
     "doccmd==2025.12.13",
     "docformatter==1.7.7",
     "freezegun==1.5.5",
-    "furo==2025.9.25",
+    "furo==2025.12.19",
     "interrogate==1.7.0",
     "mypy[faster-cache]==1.19.1",
     "mypy-strict-kwargs==2025.4.3",