Bump sphinx-substitution-extensions from 2025.11.17 to 2025.12.15

Bumps [sphinx-substitution-extensions](https://github.com/adamtheturtle/sphinx-substitution-extensions) from 2025.11.17 to 2025.12.15.
- [Release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases)
- [Changelog](https://github.com/adamtheturtle/sphinx-substitution-extensions/blob/main/CHANGELOG.rst)
- [Commits](adamtheturtle/sphinx-substitution-extensions@2025.11.17...2025.12.15)

---
updated-dependencies:
- dependency-name: sphinx-substitution-extensions
  dependency-version: 2025.12.15
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pyproject.toml

@@ -69,7 +69,7 @@ optional-dependencies.dev = [
     "sphinx-inline-tabs==2023.4.21",
     "sphinx-lint==1.0.2",
     "sphinx-pyproject==0.3.0",
-    "sphinx-substitution-extensions==2025.11.17",
+    "sphinx-substitution-extensions==2025.12.15",
     "sphinxcontrib-spelling==8.0.2",
     "ty==0.0.1a34",
     "types-pyyaml==6.0.12.20250915",