mocpy: Add version 0.20.0

[luhenry]

• Package: mocpy
• Version: 0.20.0
• Source: https://github.com/cds-astro/mocpy
• Docs: https://cds-astro.github.io/mocpy/

Compiles the PyO3/maturin Rust extension (statically linking the moc and cdshealpix crates) once per interpreter. Upstream publishes no riscv64 wheel.

Mirrors upstream's deploy.yml and the pytest run of test.yml.

Differs from upstream

• musllinux dropped - numpy has no musllinux riscv64 wheel.

Matrix: cp312/cp313/cp314 - upstream ships no free-threaded wheel.

Testing

• .[dev,plots] test deps minus ruff, pre-commit and pytest-cov - lint/coverage tooling only.
• Runs against the installed wheel with resources/ staged as the working directory.
• test_read_fits_file deselected - it finds resources/ through the source-checkout layout.
• Test deps regions (regions: Add version 0.12 #3115) and cdshealpix (cdshealpix: Add version 0.8.1 #3224) are not on the registry yet; draft until both publish.

License: OK

Verified locally on x86_64 against the built wheel; 235 passed, 1 deselected.

[luhenry]

CI failure on this run: Build mocpy 0.20.0 cp313-manylinux_riscv64 failed, but not on the compiled extension this PR adds — the wheel built, auditwheel-repaired, and installed cleanly. The failure is in the test step's pip install pytest pytest-mock requests regions cdshealpix matplotlib networkx:

ERROR: Could not find a version that satisfies the requirement regions (from versions: none)
ERROR: No matching distribution found for regions

This is the blocker already called out in the PR description: regions (#3115) and cdshealpix (#3224) aren't on the registry yet, so this PR's own test dependencies 404. Not a bug in mocpy's own build — no fix to port since neither blocking PR has merged. Leaving this draft and watched; will re-check once either lands.