[jaypantone]

Make Python 3.15 the primary version for linting, type checking, packaging, and Linux/macOS/Windows tests. Keep Linux compatibility coverage for CPython 3.11–3.14 and PyPy 3.11, and add a required PyPy 3.12 job. PyPy 3.12 is already stable (PyPy 8.0.1), so this uses the normal stable version selector.

Drop CPython and PyPy 3.10 support for the next release: require Python >=3.11, remove the 3.10 jobs and tox environments, update classifiers, target Python 3.11 in Black, and document the change in the README and changelog.

The previous workflow installed development dependencies outside tox, where isolated environments could not use them, while tox unconditionally reinstalled development CSS even for release checks. Select both CSS and Permuta inside tox instead: master and PRs targeting it use PyPI releases; other branches use both development branches. Apply this consistently to pytest, mypy, and pylint. Install pycparser and setuptools only in PyPy test environments to satisfy the dependencies of its bundled cffi and HPy packages; the first hosted run exposed this during pip check.

Also update checkout and setup-python to v7 in both workflows, enable pip caching and cancellation of superseded runs, add manual dispatch and a job timeout, configure weekly Dependabot updates for Actions, and align the Black pre-commit pin with tox. Remove obsolete pylint configuration and use ValueError for three invalid-input paths without suppressing the exception checks.

Validation:

• All four lint/type checks pass on Python 3.15; actionlint passes.
• Python 3.15 builds both the wheel and source distribution; twine check passes for both. Wheel metadata confirms Python >=3.11.
• Full suites passed earlier in this PR on Python 3.14 with development dependencies and Python 3.15 with released dependencies: 3,719 tests each.
• All 28 tests covering the invalid-input exception cleanup passed.
• Verified that all 13 workflow jobs map to tox environments and that development dependencies are actually installed from their Git branches inside tox.
• Stable PyPy 3.12 with development dependencies: all 3,719 tests passed locally.
• All 13 jobs in the hosted PR matrix pass, including Python 3.15 on Linux/macOS/Windows and PyPy 3.11/3.12. The push run also passed.
• The PR PyPy 3.12 job needed one retry after a TLS-handshake timeout contacting permpal.com; the same commit passed on the retry, in the parallel push run, and locally.

[ulfarsson]

Looks good, except for all the testing stuff in the readme