* Switch development dependencies to Pipenv lockfile

- add Pipfile and Dependabot-compatible Pipfile.lock
- update lint, tox, CI, Travis, and Makefile workflows
- support Python 3.10 through 3.14
- remove the pip-tools requirements lockfile
- standardize linting, type checking, and tests

* Streamline GitHub Actions CI workflow

- consolidate duplicate lint and PR workflows
- run strict linting, type checking, and tests
- test against Python 3.10 through 3.14
- install dependencies from Pipfile.lock
- add caching, timeouts, minimal permissions, and concurrency control
- remove ignored failures and fragile changed-file logic

Bumps [pipx](https://github.com/pypa/pipx) from 1.16.2 to 1.16.5.
- [Release notes](https://github.com/pypa/pipx/releases)
- [Changelog](https://github.com/pypa/pipx/blob/main/docs/changelog.rst)
- [Commits](pypa/pipx@1.16.2...1.16.5)

---
updated-dependencies:
- dependency-name: pipx
  dependency-version: 1.16.5
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>