Drop Python 3.10, test Python 3.11 to 3.14 in CI

[aaronspring]

Description

Follows xarray's Python support window, as xskillscore did in xarray-contrib/xskillscore#469. Python 3.10 is dropped, and CI now tests Python 3.11 through 3.14.

• pyproject.toml: requires-python = ">=3.11", classifiers 3.11–3.14, black target-version py311–py314, pyproject-fmt max_supported_python = "3.14"
• ci.yml: the pull-request matrix runs 3.11 and 3.14; the scheduled, workflow_dispatch and full-ci runs cover 3.11, 3.12, 3.13 and 3.14. Coverage is measured and uploaded from the 3.14 maximum-test-conda entry. Doctests and notebooks run on 3.11.
• benchmarks.yml: 3.11. upstream-dev.yml: 3.14.
• conda envs: python >=3.11,<3.15; the docs env uses >=3.11,<3.12
• Minimum dependency pins are unchanged.
• CHANGELOG has a breaking-change entry, and AGENTS.md (the target of the CLAUDE.md symlink) is updated.

Two fixes follow from the newer dependency versions that Python 3.11 resolves:

• Doctest reprs: on 3.10 the resolver stopped at xarray 2025.6.1; on 3.11 it now gets xarray 2026.7, which orders coordinates differently in reprs. The expected doctest output in classes.py, metrics.py and utils.py is updated. Only the order of lines changes; no values change.
• Read the Docs: the docs environment now resolves Sphinx 9 and sphinx-llm 1.1. sphinx-llm warns on bibtex citation and abbreviation nodes, and fail_on_warning turned those warnings into a failed build. conf.py now suppresses those two node types (the HTML is unaffected) and sets llms_txt_full_build = True, because sphinx-llm 1.1 no longer writes llms-full.txt by default.

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• pre-commit run --all-files passes, including GitHub workflow schema validation.
• Doctests were reproduced and fixed locally on Python 3.11 with xarray 2026.7.0.
• The docs were built locally in the conda environment from ci/requirements/docs.yml with no warnings; both llms.txt and llms-full.txt are generated.
• CI (Python 3.11 and 3.14, pip and conda, doctests, notebooks) and Read the Docs pass. Add the full-ci label to run the whole 3.11–3.14 matrix on all operating systems.

Checklist (while developing)

• CHANGELOG is updated with reference to this PR.

References

• Drop Python 3.10, support 3.11 to 3.14 following xarray xarray-contrib/xskillscore#469

🤖 Generated with Claude Code

https://claude.ai/code/session_01S4BXUfDCfzQsK8kyRmu4ox

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.27%. Comparing base (0569861) to head (7149d2d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #932   +/-   ##
=======================================
  Coverage   91.27%   91.27%           
=======================================
  Files          59       59           
  Lines        6548     6548           
=======================================
  Hits         5977     5977           
  Misses        571      571           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.