#19 .github/workflows: Migrate workflows to Blacksmith runners

This PR has been automatically generated by a team member in your GitHub organization using Blacksmith's Migration Wizard. This PR changes the following:

1. Your selected workflows will now run on Blacksmith's 2x faster hardware (e.g., runs-on: blacksmith-4vcpu-ubuntu-2204). Learn more about the different instances available to choose from.
2. Your jobs running on Blacksmith will now have all official GitHub and popular third-party cache actions automatically interact with our 4x faster, colocated cache. Learn more about Blacksmith's actions cache.
3. Your GitHub Actions will now actually be observable. Learn more about Blacksmith's logging and other observability features.
4. Your Docker builds will now automatically share their Docker layer cache, resulting in up to 40x faster builds. Learn more about Blacksmith's Docker layer caching.

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Summary by cubic

Migrated all GitHub Actions workflows to Blacksmith runners to speed up CI and enable colocated caching and observability. Updated runner tags to blacksmith-4vcpu-ubuntu-2404 and the Windows shims job to blacksmith-4vcpu-windows-2025; no workflow logic changes.

• Refactors
  • Replaced runs-on: ubuntu-latest with runs-on: blacksmith-4vcpu-ubuntu-2404 across CI, release, audit, CodeQL, PR, and Node integration workflows.
  • Switched Windows shims tests from windows-latest to blacksmith-4vcpu-windows-2025.