build(deps-dev): bump shibuya from 2026.1.9 to 2026.5.19

Bumps [shibuya](https://github.com/lepture/shibuya) from 2026.1.9 to 2026.5.19.
- [Release notes](https://github.com/lepture/shibuya/releases)
- [Changelog](https://github.com/lepture/shibuya/blob/main/docs/changelog.rst)
- [Commits](lepture/shibuya@2026.1.9...2026.5.19)

---
updated-dependencies:
- dependency-name: shibuya
  dependency-version: 2026.5.19
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

pyproject.toml

@@ -79,7 +79,7 @@ dev = [
 ]
 docs = [
   "myst-parser==5.0.0 ; python_version >= '3.12'",
-  "shibuya==2026.1.9 ; python_version >= '3.12'",
+  "shibuya==2026.5.19 ; python_version >= '3.12'",
   "sphinx==9.1.0 ; python_version >= '3.12'",
   "sphinx-copybutton==0.5.2 ; python_version >= '3.12'",
   "sphinx-new-tab-link==0.8.1 ; python_version >= '3.12'",