Add Windows ARM64 build

[ndabas]

Problem

The package does not install on Windows ARM64 machines, if build tooling is not installed.

Solution

As the title says, added Windows ARM64 builds to CI.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

CI is passing, I did a smoke test on the built wheels on my Windows ARM64 machine.

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Note

Low Risk
CI and documentation only; no runtime or auth changes. Release jobs could fail if the new runner leg is flaky, but that does not affect already-shipped packages.

Overview
Adds Windows on ARM64 (aarch64-pc-windows-msvc) to the cross-platform wheel build matrix so published wheels install on Windows ARM64 without a local Rust build.

The new leg runs on windows-11-arm in dev publish, RC/prod release, and release readiness workflows—the same maturin targets as the existing Windows x64 job. Collect/publish validation now expects 8 abi3 wheels (was 7) so a missing ARM64 artifact fails the pipeline.

Installation docs now state that Windows wheels cover x86-64 and arm64, matching what CI ships.

^{Reviewed by Cursor Bugbot for commit a2e6d82. Bugbot is set up for automated code reviews on this repo. Configure here.}