chore: stop support py3.9, now support py3.10-3.15

[mdevolde]

chore: stop support py3.9, now support py3.10-3.15

Why the pull request was made

To follow python releases and stop supporting python 3.9 as it is an EOL version since 2025, and it represents around 1.5% of the lib downloads.
By upgrading the minimum python version to 3.10, we ensure that our library can use the most recent versions of each dependencies, and of the type checker, mypy, that doesn't support anymore python 3.9 since it's v2.

Summary of changes

• Upgrade minimum version of language_tool_python to 3.10 (and edited lib classifiers).
• Remove testing for python 3.9 and added testing for python 3.15.
• Remove import of TypeGuard from typing_extensions (can be imported from typing since python 3.10).
• Remove last Union usages (since python 3.10 fully support | operator for typing).
• Edit docs to support these changes.
• Upgrade uv.lock to remove old constraints due to python 3.9.

Screenshots (if appropriate):

Not appropriate.

How has this been tested?

Applied local tests (including with python 3.15).

Resources

Python releases: https://www.python.org/downloads/

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, checked types and tests.

[Copilot]

Pull request overview

This PR updates language_tool_python to drop Python 3.9 support (now EOL) and set Python 3.10 as the minimum supported version, aligning packaging metadata, CI, and internal typing/compat code accordingly.

Changes:

• Bump minimum supported Python to >=3.10 across packaging metadata and documentation.
• Update CI matrix to stop testing Python 3.9 and add Python 3.15 on Ubuntu.
• Simplify typing/compat code by removing Python 3.9-era Union/typing_extensions.TypeGuard workarounds and adjusting lockfile markers.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
uv.lock	Updates lock metadata/markers for >=3.10 and removes Python 3.9-era conditional packages/markers.
README.md	Updates stated supported/tested Python versions to >=3.10 / up to 3.15.
pyproject.toml	Sets requires-python = ">=3.10", updates classifiers, and simplifies mypy dependency marker.
Makefile	Removes runtime Python version gating for mypy; (contains a small recipe formatting issue).
make.bat	Removes runtime Python version gating for mypy on Windows batch script.
language_tool_python/match.py	Replaces Union[...] with `
language_tool_python/config_file.py	Replaces Union[...] with `
language_tool_python/api_types.py	Switches TypeGuard import to typing.TypeGuard for 3.10+.
language_tool_python/_compat.py	Removes TypeGuard compatibility export; keeps deprecated and toml_loads.
.github/workflows/test.yml	Removes Python 3.9 from matrix and adds Python 3.15 on Ubuntu.

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