why: Cut the next alpha covering the theme-flicker fix branch
(initial-load FOWT prevention, Cloudflare Rocket Loader bypass for
inline scripts, synchronous no-js removal, and removal of theme-
blending CSS transitions on `.sig` and `dl.py` headers).

what:
- just bump-version 0.0.1a11: every workspace package's
  pyproject.toml version, every __init__.py / extension.py
  __version__, the workspace pyproject.toml, scripts/ci helpers
  and matching test, and uv.lock all advance to 0.0.1a11.
- CHANGES gains a dated "## gp-sphinx 0.0.1a11 (2026-04-26)"
  release header above the existing Bug fixes content; the
  "## gp-sphinx 0.0.1 (unreleased)" placeholder + maintainer
  comment stays at the top of the file as the next-release
  insertion point.