chore: drop Python 3.9, require 3.10+

[henryiii]

🤖 AI text below 🤖

Addresses part of #1132.

Python 3.9 reached EOL in October 2025. This PR drops 3.9 support, bumping the minimum to Python 3.10, and applies the modernizations that unlocks.

Changes

pyproject.toml

• requires-python = ">=3.10" (was >=3.9)
• numpy >=1.21.3 (oldest numpy with a 3.10 wheel; was >=1.21)
• Added explicit Programming Language :: Python :: 3.10/3.11/3.12/3.13 classifiers
• [tool.cibuildwheel]: removed cp39-musllinux_i686 skip entry (replaced with cp310-musllinux_i686)
• [[tool.cibuildwheel.overrides]]: selector changed from cp3{9,10}-manylinux* to cp310-manylinux*

.github/workflows/release.yml

• Removed cp39 from the py: matrix
• Removed two cp39 excludes (ubuntu-24.04-arm and windows-11-arm)

.github/workflows/test.yml

• Minimum-version test leg updated from python-version: "3.9" / numpy==1.21.0 to python-version: "3.10" / numpy==1.21.3

noxfile.py

• No changes needed: MINIMUM_PYTHON reads from pyproject.toml dynamically, so it picks up 3.10 automatically.

Typing modernization (src/iminuit/)

• typing.py: removed Optional, Union, List imports; Key type alias and UserBound/Interval fields now use X | Y and float | None syntax; added from __future__ import annotations
• ipywidget.py, qtwidget.py: from typing import Dict, Callable replaced with collections.abc.Callable and dict[str, Any]
• Ruff UP auto-fixes applied across src/ (213 fixes): deprecated typing.Union, Optional, List, Tuple, Dict, Set usages replaced with modern equivalents in minuit.py, cost.py, util.py, _deprecated.py, _optional_dependencies.py, _parse_version.py, _repr_html.py; unused typing imports removed (F401)
• One correctness fix in minuit.py: method: str | Callable | None = None (ruff correctly surfaced a latent mypy issue)

doc/conf.py

• Synced root_version to match the submodule SHA (pre-commit hook was failing on a pre-existing mismatch)

Test results

All tests pass on Python 3.10 except tests/test_tabulate.py::test_params which is a pre-existing failure on the develop branch (tabulate column-alignment difference unrelated to this PR).

Note on conflicts

This PR modifies minuit.py, cost.py, and util.py (import blocks only, not logic). It may conflict slightly with parallel bugfix PRs touching those same files. Recommend merging this PR last among active PRs, or rebasing it on top of them once they land.

[henryiii]

Ahh, I've been trying to remember to tell it not to do a Python drop, missed this one had that recommendation. If this is helpful, we can leave it open, if you prefer to do it yourself eventually, happy to close. (I have a custom skill that can be used for Python drops, too, at https://github.com/henryiii/skills).