fix: only decode URL hash instead of entire URL

[eltigerchino]

quick fix for #13321 (hopefully before #13316 is released)

This PR ensures only the hash of the URL is decoded so that any encoded hash character in the query parameters remains encoded.

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[Rich-Harris]

preview: https://svelte-dev-git-preview-kit-13332-svelte.vercel.app/

this is an automated message