Adopt TypeScript under Node 24

[Bo98]

GitHub Actions now supports Node 24. Node 24 supports natively running TypeScript without needing a compile stage (erasable syntax only) which means we can adopt it without needing to add any build stages.

This pull request experiments with adopting TypeScript (for one action in this initial draft).

Given the Actions runner with support for Node 24 is just 2 weeks old, perhaps we want to allow a little more time before doing this since we don't do tagged releases?