RTD builds were failing because openblas-build 0.10.16 (transitively pulled by
ndarray-linalg via openblas-src) requires ureq tls feature flags it does not
enable. Cargo.lock is gitignored so RTD always resolves fresh and hits the
broken upstream version.
Building the Rust extension on RTD is unnecessary: the Sphinx pages do not
use autodoc against the Python module, and all inline plots under doc samples
are pre-rendered PNGs committed to docs/source/_static/auto/ by the local
scripts/inject_doc_plots.py author-time pipeline.
This commit makes the RTD job render-only: install docs/requirements.txt and
run Sphinx. No Rust toolchain, no maturin, no OpenBLAS.
ThotDjehuty