Add Python 3.14 to CI testing matrix

[Copilot]

Adds Python 3.14 to conda package CI testing and updates single-version CI jobs from 3.13 to 3.14.

Changes

• build_workflow.yml: Added 3.14 to test matrix; updated pre-commit job to use 3.14
• docs_workflow.yml: Updated docs publishing to use 3.14
• pre_commit_update_workflow.yml: Updated auto-update job to use 3.14
• conda_package/ci/: Added linux_64_python3.14.____cpython.yaml and osx_64_python3.14.____cpython.yaml configs
• pyproject.toml: Added Python 3.14 classifier

The CI now tests against Python 3.10, 3.11, 3.12, 3.13, and 3.14. All jobs that previously ran on a single Python version (3.13) now run on 3.14.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add Python 3.14 to conda package CI testing</issue_title>
<issue_description>We want to add python 3.14 to the CI testing and make sure any CI that runs on only one python version uses 3.14 (instead of 3.13).</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add Python 3.14 to conda package CI testing #692

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[xylar]

We're stuck for now because conda and conda-build are not yet available for python 3.14, see conda-forge/conda-feedstock#274

[xylar]

A temporary solution would be to install conda and conda-build into an environment for an older version of python and only install the package itself into a separate environment with the newer python, but that doesn't seem worth the bother for now. We can return to this PR when conda is available.

[xylar]

Okay, we finally got this working!