Fix RTD build failure: remove --system flag from uv pip install

The --system flag installs packages into the global Python (/home/docs/.asdf/installs/python/3.14.0)
instead of the RTD virtualenv. When Sphinx runs from the virtualenv, it cannot find sphinx_rtd_theme,
causing a ModuleNotFoundError.

Without --system, uv respects the VIRTUAL_ENV env var that RTD sets during post_create_environment
hooks, installing packages into the virtualenv where Sphinx can find them.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: matagus

.readthedocs.yaml

@@ -12,7 +12,7 @@ build:
       # Install uv
       - pip install uv
       # Install dependencies with docs extras
-      - uv pip install --system -e ".[docs]"
+      - uv pip install -e ".[docs]"
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx: