chore: bump typescript to 5.5

[Rich-Harris]

TypeScript 5.5 is a huge release with a ton of improvements. Most notably for us, as weirdos who use JSDoc, is that we can now use @import declarations. This will make our code vastly less cluttered (though we can do that incrementally in follow-up PRs — this is just groundwork).

AFAICT the version of TypeScript we use internally shouldn't have any impact on consumers, though I haven't studied the changed output in the generated .d.ts files.

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• Ideally, include a test that fails without this PR but passes with it.

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

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