Modernize wheel CI and add cp314 wheel support

[Mokto]

Summary

PyPI currently has wheels for hdbscan 0.8.42 covering cp310–cp313 on
Linux/macOS/Windows, but the pythonpublish_wheel.yml workflow that's
checked in doesn't actually produce them — it still pins cython<3 inside
a manylinux2014 container and only matrices cp38–cp311. The current
wheels must have been built out-of-band (cibuildwheel locally, or via a
workflow tweaked at release time and never committed). cp314 wheels haven't
been published yet, and the workflow as-checked-in can't produce them
either: Python 3.14 needs glibc ≥ 2.28 and refuses to compile against
Cython 2.

This PR brings the committed workflow into a state where simply dispatching
it for the next release produces a complete, current wheel set — including
cp314.

Build system (pyproject.toml)

• [build-system] now requires cython>=3.0.11,<4 and numpy>=2.0,<3 so
  any source build (CI, conda-forge, end-user pip install) targets
  current Cython/NumPy.
• requires-python = ">=3.10" matches the supported matrix — Python 3.8
  reached EOL on 2024-10-07 and 3.9 on 2025-10-31.
• Adds the Programming Language :: Python :: 3.14 classifier.

Cython 3 source updates

• Reorders nogil except -1 → except -1 nogil across .pyx/.pxd
  (Cython 3 syntax requirement).
• Adds # distutils: define_macros=NPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION
  to silence NumPy deprecated-API warnings.

This rebases the still-relevant source-file hunks of #691 onto current
master.

Wheel CI (.github/workflows/pythonpublish_wheel.yml)

• Linux: manylinux2014_x86_64 → manylinux_2_28_x86_64 (Python 3.14
  needs glibc ≥ 2.28). Pins cython>=3.0.11,<4 and numpy>=2.0 in the
  build env, installs setuptools+wheel (the cp314 image doesn't ship
  them by default), and extends the matrix to cp310–cp314.
• Windows/macOS: replaces deprecated oldest-supported-numpy with
  numpy>=2.0, bumps actions/checkout v1→v4 and actions/setup-python
  v1→v5 (v1 doesn't support recent Pythons), retires the EOL
  windows-2019 / macos-11 runners (now windows-2022 + macos-14 —
  macOS 14 already produces universal2 wheels covering arm64 and x86_64),
  extends the matrix to 3.10–3.14, and enables allow-prereleases: true
  for 3.14.
• Disables fail-fast on both matrices so one failure doesn't cancel the
  rest.

Verification

• All 15 build jobs (Linux cp310–cp314, Windows + macOS for 3.10–3.14) go
  green on a workflow_dispatch run on the author's fork.
• Locally on Python 3.14.4 with Cython 3.2.4 + NumPy 2.4.4: every extension
  cythonizes and compiles cleanly, and HDBSCAN().fit(X) runs end-to-end.

Consistent with how conda-forge already ships working py314 builds.
Relates to #688, #686 (the underlying Linux wheels for 3.12/3.13 are
already on PyPI, but a future release using this workflow won't need
out-of-band builds). Supersedes #691 for the parts still relevant.

[Mokto]

The PR is ready for review.

[lmcinnes]

If you can make Cython 3 work that would be great. I'll have to run some local testing to make sure this all works, so please give me some time to manage to get to that, but this looks very promising.

[Mokto]

👍 for those who need a temporary fork in the meantime, I've created https://pypi.org/project/hdbscan-314/0.8.42/

I'll delete it this is merged & released.

Works for us in production