Modernize packaging and add type hints

[craigds]

• Migrate from setup.py to pyproject.toml
• Support Django 4.2/5.2/6.0, Python 3.8-3.13
• Add type hints and py.typed marker
• Add ruff linting and mypy type checking
• Update CI to use uv

[Copilot]

Pull request overview

This PR modernizes the django-fieldsignals package by migrating from setup.py to pyproject.toml-based packaging, adding comprehensive type hints throughout the codebase, and updating CI/CD infrastructure. The changes aim to improve maintainability, provide better IDE support through type annotations, and support contemporary Python and Django versions.

Key changes:

• Migrated packaging from setup.py to pyproject.toml following PEP 621 standards
• Added comprehensive type hints with mypy strict mode and py.typed marker for type checking support
• Updated supported versions to Python 3.8-3.13 and Django 4.2+, with references to unreleased Django 5.2/6.0 (needs correction)

Reviewed changes

Copilot reviewed 11 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pyproject.toml	Complete migration to modern pyproject.toml with build configuration, dependencies, and tool settings for ruff, mypy, and pytest. References Django 5.2/6.0 which don't exist yet.
setup.py	Removed in favor of pyproject.toml
tox.ini	Updated test matrix for Python 3.8-3.13 and Django 4.2/5.2/6.0, added mypy environment. References nonexistent Django versions.
fieldsignals/signals.py	Added comprehensive type hints with TYPE_CHECKING imports, updated to use f-strings, and modernized super() calls
fieldsignals/tests/test_signals.py	Added type hints to all test functions and helper classes, changed tuple to list for fields parameters, replaced django.utils.timezone.utc with datetime.timezone.utc
fieldsignals/init.py	Added type imports, all export list, and changed version to string format
fieldsignals/tests/settings.py	New minimal Django settings file for testing and django-stubs
fieldsignals/tests/init.py	Removed test exports since pytest discovers tests automatically
fieldsignals/py.typed	New empty marker file indicating the package supports type checking
MANIFEST.in	Removed (no longer needed with pyproject.toml)
CLAUDE.md	New documentation file with project overview and command reference
.gitignore	Added entries for ruff cache, uv.lock, and Claude settings
.github/workflows/test.yml	Updated to use uv for dependency management, added separate lint job, updated action versions, and expanded Python version matrix

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[Copilot]

The py.typed marker file needs to be explicitly included in the package. Add a [tool.setuptools.package-data] section with: fieldsignals = ["py.typed"] to ensure the type marker is included in the distribution. Without this, type checkers won't recognize this package as typed.

Suggested change

	[tool.setuptools.package-data]
	fieldsignals = ["py.typed"]

[Copilot]

Missing Python 3.9 and 3.11 classifiers. The project should either include these versions in testing and classifiers, or explicitly document why they are skipped.

Suggested change

	"Programming Language :: Python :: 3.8",
	"Programming Language :: Python :: 3.10",
	"Programming Language :: Python :: 3.8",
	"Programming Language :: Python :: 3.9",
	"Programming Language :: Python :: 3.10",
	"Programming Language :: Python :: 3.11",