why: hotfix release — sphinx-gp-llms was missing from gp-sphinx
runtime dependencies, breaking consumer docs builds.

what:
- Add sphinx-gp-llms to gp-sphinx dependencies
- Bump all workspace packages 0.0.1a24 → 0.0.1a25
- CHANGES dated 2026-05-25, next unreleased is 0.0.1a26