chore: faster CI

[Rich-Harris]

I have a hunch that there are several things we can be doing to improve the time it takes to run CI. I asked an agent to find the lowest-hanging fruit and this is what it came up with — mostly enabling more parallelism, though it did also remove Node 22 from the e2e test matrix, which is possibly dangerous. Let's see how much this buys us

[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 1a86305:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/1a8630501fa7351e842e69d5becf49c772290f21

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16842

[changeset-bot]

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-16842-svelte.vercel.app/

[teemingc]

There's also a setting for '50%' workers, etc. to adjust to the number of cores the runner has rather than a strict number

I also suspect there may be some tests we're running in multiple suites which we can deduplicate but I haven't looked deeply into it.

Removing Node 22 for test-kit probably frees up a good number of runners. Those are currently the longest tests