Infra updates

[awdeorio]

Modernize packaging and CI

Closes #42.

Replaces setup.py with pyproject.toml (PEP 517/518) and modernizes the supporting build, test, and CI configuration. Along the way, fixes a few failures caused by newer versions of click and pylint so the suite is green again.

Packaging (#42)

• Add pyproject.toml with the setuptools build backend. Migrates all metadata from setup.py, declares runtime dependencies, the agio console script, and a single consolidated dev extra (the old dev and test extras are merged, matching the sibling madoop repo).
• Remove setup.py.
• MANIFEST.in: include *.md so the docs ship in the sdist, and drop a stale include test line. check-manifest passes.
• Update the release procedure in CONTRIBUTING.md: edit and grep pyproject.toml instead of setup.py, and build with python -m build instead of python setup.py sdist bdist_wheel.

Python versions and CI

• requires-python = ">=3.10", dropping end-of-life Python versions and matching the floor used in mailmerge.
• Zero-maintenance CI version handling: the matrix runs ["3.x"] (always the latest Python) and the job runs tox -e py3. This drops tox-gh-actions and the hardcoded [gh-actions] version map, so no file needs editing when a new Python is released.
• tox.ini: envlist = py3; the lint and test commands are unchanged.
• Bump GitHub Actions: actions/checkout@v4, actions/setup-python@v5, and codecov/codecov-action@v4 (now passing token and slug).
• Fix an inaccurate workflow comment ("push to master" to "push to main or develop").

Dependency-drift fixes

These are unrelated to packaging but were breaking the suite with current dependency versions:

• tests/test_cli.py: drop mix_stderr=False, removed from CliRunner in click 8.3 (separate stdout/stderr is now the default).
• agiocli/api_client.py: use yield from in get_paginated (pylint use-yield-from).
• agiocli/__main__.py: add too-many-positional-arguments to the existing pylint disables on the Click subcommands.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.70%. Comparing base (2dd78fc) to head (09c0489).

Files with missing lines	Patch %	Lines
agiocli/api_client.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #46      +/-   ##
===========================================
+ Coverage    72.55%   72.70%   +0.15%     
===========================================
  Files            4        4              
  Lines          481      480       -1     
===========================================
  Hits           349      349              
+ Misses         132      131       -1     

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