Vouch request for ShiroKSH #4262

Why do you want to contribute?

I'd like to fix #2490. retry.fetch currently drops valid Headers, tuple-array, and Request headers while adding x-retry-count, which can remove authorization and content-type headers. I plan to preserve native fetch header semantics and add a focused local HTTP server regression test.

Prior contributions or relevant experience

GitHub profile: https://github.com/ShiroKSH