py(deps[docs]): Pin sphinx<9 to avoid breaking changes

why: Sphinx 9.x introduced breaking changes that affect sphinxarg/ext.py
(mock() function moved to internal _dynamic package) and mypy fails on
PEP 695 type statement syntax. Sphinx 9 also drops Python 3.10/3.11 support
(requires Python 3.12+).
what:
- Add sphinx<9 constraint to dev and docs dependency groups
- Update uv.lock to use sphinx 8.x

Author: tony

pyproject.toml

@@ -58,7 +58,7 @@ dev = [
   # Docs
   "aafigure",
   "pillow",
-  "sphinx",
+  "sphinx<9",
   "furo",
   "gp-libs",
   "sphinx-autobuild",
@@ -92,7 +92,7 @@ dev = [
 docs = [
   "aafigure",
   "pillow",
-  "sphinx",
+  "sphinx<9",
   "furo",
   "gp-libs",
   "sphinx-autobuild",