[shunt16]

Brings obsarray's package-level setup in line with the newer MetEOR tools (eomatch, eoio, …). CI on main currently fails at "Install dependencies" on every job; this replaces it with a working setup, and fixes the issues the new checks and current numpy/xarray turned up.

Tooling

• pyproject.toml only: removed setup.py, requirements.txt, tox.ini and environment.yml. Dev/docs dependencies are now the [dev] and [docs] extras, and pytest config lives in pyproject.toml.
• Versioning: replaced versioneer with setuptools_scm (version from v* tags), with __version__ read via importlib.metadata.
• Lint/format: replaced black with pinned ruff (check and format) and mypy in pre-commit, with an explicit ruff rule selection. The mypy hook installs numpy/xarray and is scoped to obsarray/, so it reports the same results as CI.
• GitHub Actions:
  • tests.yml runs pytest on Python 3.11–3.13 and uploads test/coverage reports and coverage to Codecov. A separate lint job runs ruff format --check, ruff check and mypy.
  • publish.yml publishes to PyPI on a v* tag push (or a confirmed manual run), via trusted publishing.
• Read the Docs: installs .[docs] and fetches full history so setuptools_scm sees the tags.
• Python ≥ 3.11 (3.8–3.10 are end-of-life).
• README: new badges, development and release instructions, and the licence corrected to LGPLv3.

Fixes needed to get CI green

• NumPy 2 flag overflow: setting a flag to False raised OverflowError, which also broke the docs build. This is fixed by cherry-picking @mattgoalen's two fix commits from overflow-errors.
• test_rename_dims: newer xarray's assert_identical also compares indexes, so the test now drops the retained time index before comparing. This was a test issue, not a library bug.
• ruff and mypy findings: fixed in separate commits. They're mostly annotation-only; the small behaviour changes are listed in the "Fix mypy findings" commit message.
• Formatting: a mechanical ruff format commit. It keeps black's 88-column line length rather than the template's 120, to avoid reflowing about 650 lines and conflicting with open branches.
• Sphinx config: language = None changed to "en".

Testing

Run locally on Python 3.13 (numpy 2.5, xarray 2026.9):

• All 173 tests pass.
• ruff check, ruff format --check and mypy obsarray are clean, and pre-commit run -a passes.
• The sdist and wheel build, with the version taken from tags.
• The Sphinx HTML docs build. The remaining warnings are pre-existing and cosmetic.

Before the first release

• Register a PyPI trusted publisher with owner comet-toolkit, repository obsarray, workflow publish.yml, environment pypi.
• Add a CODECOV_TOKEN repository secret if you want coverage uploads.

Not changed

• Docs stay on Read the Docs: no GitHub Pages docs.yml, because obsarray.readthedocs.io is the published URL.
• No .gitlab-ci.yml, since obsarray is GitHub-only.
• The license classifier is kept. setuptools warns that it's deprecated in favour of SPDX, but choosing between LGPL-3.0-only and LGPL-3.0-or-later is a licensing decision.
• The old CI turned the coverage report into a PDF for the quality documentation. The new workflow uploads the HTML report as an artifact instead.