LaTeX writer tests fail with Docutils HEAD

### Describe the bug @jfbu Recent changes in Docutils make the LaTeX writer tests fail (Docutils commit r10284 from 2026-01-07). From Docutils RELEASE NOTES: > LaTeX writer: > - Do not write ``\label`` commands for section titles and other > implicit targets if there is no matching reference in the document. You may either * change the Sphinx LaTeX writer to write all labels, or * adapt the tests (my preference): FAILED tests/test_builders/test_build_latex.py::test_latex_labels expected: \caption{labeled figure}\label{\detokenize{index:id1}}\label{\detokenize{index:figure2}}\label{\detokenize{index:figure1}}\end{figure} result: \caption{labeled figure}\label{\detokenize{index:id2}}\label{\detokenize{index:figure2}}\label{\detokenize{index:figure1}}\end{figure} Solutions: a) use special ID numbers only for Docutils 0.22 - if docutils.__version_info__[:2] < (0, 22): + if docutils.__version_info__[:2] == (0, 22): figure_id, table_id = 'id1', 'id2' else: figure_id, table_id = 'id2', 'id3' b) set "auto-id-prefix" to "%" for more stable IDs FAILED tests/test_builders/test_build_latex.py::test_latex_raw_directive expected: \label{\detokenize{index:id1}} standalone raw directive (LaTeX) result: standalone raw directive (LaTeX) Solution: change the source to contain a reference to the label or remove the label from the assertion statement. FAILED tests/test_builders/test_build_latex.py::test_writer expected \begin{sphinxfigure-in-table} \centering \capstart \noindent\sphinxincludegraphics{{img}.png} \sphinxfigcaption{figure in table}\label{\detokenize{markup:id8}}\end{sphinxfigure-in-table}\relax result \begin{sphinxfigure-in-table} \centering \capstart \noindent\sphinxincludegraphics{{img}.png} \sphinxfigcaption{figure in table}\label{\detokenize{markup:id7}}\end{sphinxfigure-in-table}\relax Solution: change the source to contain a reference to the label or adapt ID numbers. ### How to Reproduce See e.g. https://github.com/sphinx-doc/sphinx/actions/runs/24500180813/job/71604629131?pr=14400#logs and https://github.com/sphinx-doc/sphinx/pull/14399 ### Environment Information ```text Docutils repository version (0.23.b.dev) ``` ### Sphinx extensions ```python ``` ### Additional context _No response_