chore: move scroll restoration and focus reset out of client.js

[Nic-Polumeyv]

Scroll restoration and focus reset live in client.js but read none of its state. This moves them, unchanged, into their own module, the shape snapshots.js took in #16685.

[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 2b735ad:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/2b735adaac8d17821fccef482a97f1c91c61b1dd

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16980

[changeset-bot]

⚠️ No Changeset found

Latest commit: 2b735ad

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-16980-svelte.vercel.app/