Add native Windows ARM64 CI and release wheels

[ssss141414]

Summary

This draft adds generic Windows support directly on the current canonical master, then adds native Windows ARM64 validation and release integration in a separate commit.

• add Windows runtime, MSVC build, and targeted test support without inheriting the formatting churn from Start unifying uvloop & winloop together (WINDOWS SUPPORT) #736
• add windows-latest regression coverage and native windows-11-arm coverage for CPython 3.11.9, 3.12.10, 3.13.15, 3.14.7, and 3.14t
• build and test Windows AMD64 wheels for cp38 through cp314t
• build and test Windows ARM64 wheels for cp311 through cp314t
• verify each ARM64 wheel contains an ARM64 (0xAA64) native extension before upload
• require Windows wheel jobs before publication
• keep Windows socket assertions locale-independent by checking stable error codes

Commit structure

1. Add Windows runtime and test support
2. Add Windows ARM64 CI and release wheels

The branch is rebuilt directly from e8efea4 rather than stacked on #736. #736 remains implementation reference and attribution context, but its broad formatting history is not part of this PR.

Local validation

Native Windows ARM64, CPython 3.13.15, MSVC 14.44:

• built uvloop-0.22.1-cp313-cp313-win_arm64.whl
• clean-installed the wheel outside the source checkout
• imported the installed extension on native ARM64
• independently parsed uvloop/loop.cp313-win_arm64.pyd as PE machine 0xAA64
• ran the cibuildwheel command: 526 tests passed with 131 platform skips
• ran focused process, signal, DNS, pipe, socket, and TCP suites during reconstruction
• passed sourcecode/flake8 and mypy checks
• passed the complete canonical minimal-diff review using the vendored Ponytail skills: Lean already. Ship.

The active uvloop handle-leak test remains enabled on Windows. It rejects increasing handle counts while allowing delayed cleanup to reduce the process-wide count.

Remaining draft checks

• complete the hosted Windows AMD64 and five Windows ARM64 test rows
• complete all non-Windows regression rows
• confirm cp314t resolves the native ARM64 free-threaded interpreter
• run the release workflow matrix and confirm ARM64 artifact inspection

This remains a draft and does not claim merge, publication, or upstream acceptance.