[Code scan] Quote dependency specifier in ReadTheDocs install command

[njzjz]

This issue was found by a Codex global scan of the repository at commit 19f9265.

The ReadTheDocs install job passes deepmd-kit[torch]>=3.0.0b2 through a shell command without quoting:

deepmd-gnn/.readthedocs.yml

Lines 11 to 13 in 19f9265

	- uv venv $READTHEDOCS_VIRTUALENV_PATH
	- VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH uv pip install deepmd-kit[torch]>=3.0.0b2 --extra-index-url https://download.pytorch.org/whl/cpu
	- VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH CMAKE_PREFIX_PATH=$(python -c "import torch;print(torch.utils.cmake_prefix_path)") uv pip install -e .[docs]

In POSIX shells, > is parsed as output redirection. A minimal shell reproduction shows the command is split as deepmd-kit[torch] and redirects the remaining output into a file named =3.0.0b2.

$ printf '%s
' deepmd-kit[torch]>=3.0.0b2 --extra-index-url https://download.pytorch.org/whl/cpu
# creates file '=3.0.0b2' containing the arguments instead of passing the version specifier

This can make RTD install an unconstrained deepmd-kit[torch] requirement or fail in hard-to-read ways.

Suggested fix: quote the requirement, for example "deepmd-kit[torch]>=3.0.0b2", and consider quoting .[docs] for the same reason shells can treat brackets as glob syntax.