feat: update CI, fix POSIX locale compatibility

[mdevolde]

feat: update CI, fix POSIX locale compatibility

Why the pull request was made

Improve CI by updating it and integrating newer versions of Python, as well as ruff.

Summary of changes

• integrated UV and modernized CI actions
• added python 3.12, 3.13, 3.14 to CI
• handled 'C' and 'POSIX' locales as English fallback
• updated licence metadata (PEP 639)
• fixed inexistent file in MANIFEST.in

Screenshots (if appropriate):

Not applicable.

How has this been tested?

Full execution of the new CI.

Resources

Not applicable.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to documentation only)
• Refactor / code style update (non-breaking change that improves code structure or readability)
• Tests / CI improvement (adding or updating tests or CI configuration only)
• Other (please describe):

Checklist

• Followed the project's contributing guidelines.
• Updated any relevant tests.
• Updated any relevant documentation.
• Added comments to your code where necessary.
• Formatted your code, run the linters and tests.

[Copilot]

Pull Request Overview

This pull request modernizes the CI/CD infrastructure and improves locale handling for POSIX environments. The changes upgrade GitHub Actions workflows, update package metadata to use SPDX license identifiers, and add support for POSIX/C locale detection.

• CI/CD workflow modernization using uv package manager and updated action versions
• POSIX locale handling to default to English variants for "C", "POSIX", and "C." prefixed locale tags
• Package metadata updates to conform to PEP 639 standards for license specification

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
.github/workflows/test.yml	Modernizes CI workflow with uv, adds Python 3.12-3.14 to test matrix, updates action versions, adds separate lint job with Ruff
language_tool_python/language_tag.py	Adds POSIX locale detection to normalize "C", "POSIX", and "C." locales to English variants (en_us, en_gb, or en)
pyproject.toml	Updates license field to use SPDX identifier "GPL-3.0-only" and adds license-files specification per PEP 639
MANIFEST.in	Removes non-existent run_doctest.py from distribution manifest

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.