chore(docs): bump gp-sphinx pins 0.0.1a7 -> 0.0.1a8

why: Adopt the v0.0.1a8 release of the shared docs platform —
  argparse domain, CSS namespace unification under gp-sphinx-*,
  sphinx>=8.1 floor, typed env.domains.* accessors, autodoc layout
  and badges package renames, py.typed marker for typehints-gp.
what:
- Bump gp-sphinx, sphinx-autodoc-api-style, and
  sphinx-autodoc-pytest-fixtures from 0.0.1a7 to 0.0.1a8 across
  every dependency group / optional-dependency extra
- Refresh uv.lock against the published workspace

See also: https://pypi.org/project/gp-sphinx/0.0.1a8/

Author: tony

pyproject.toml

@@ -52,9 +52,9 @@ Changes = "https://github.com/tmux-python/libtmux/blob/master/CHANGES"
 [dependency-groups]
 dev = [
   # Docs (via gp-sphinx)
-  "gp-sphinx==0.0.1a7",
-  "sphinx-autodoc-api-style==0.0.1a7",
-  "sphinx-autodoc-pytest-fixtures==0.0.1a7",
+  "gp-sphinx==0.0.1a8",
+  "sphinx-autodoc-api-style==0.0.1a8",
+  "sphinx-autodoc-pytest-fixtures==0.0.1a8",
   "sphinx-autobuild",
   "types-docutils",
   # Testing
@@ -75,9 +75,9 @@ dev = [
 ]
 
 docs = [
-  "gp-sphinx==0.0.1a7",
-  "sphinx-autodoc-api-style==0.0.1a7",
-  "sphinx-autodoc-pytest-fixtures==0.0.1a7",
+  "gp-sphinx==0.0.1a8",
+  "sphinx-autodoc-api-style==0.0.1a8",
+  "sphinx-autodoc-pytest-fixtures==0.0.1a8",
   "sphinx-autobuild",
 ]
 testing = [