fix: port adapter-vercel's prerendered redirect fixes to adapter-static

[Nic-Polumeyv]

adapter-static's static_vercel_config is a marked copy of the adapter-vercel function (both carry a "This function is duplicated in..." comment), but two fixes only landed on the adapter-vercel side. This ports #8766 (redirect the non-trailing-slash counterpart of every prerendered page) and #12966 (match prerendered redirect sources regardless of trailing slash), so a static site deployed on Vercel gets the same redirect behavior as adapter-vercel.

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Install the latest version of @sveltejs/kit from 8ec99cd:

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Latest commit: 8ec99cd

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@sveltejs/adapter-static	Patch

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