chore: update to TypeScript 5.6

This change should have no user impact.

This updates TypeScript to the latest version, 5.6.2. It also updates
`typedoc` dependencies to their latest versions.

I verified that the generated types in `dist/` were not meaningfully
changed. (Some `Iterator` types were slightly adjusted, as expected;
[TypeScript 5.6 made some changes to how `Iterator` types work][0].)

[0]: https://devblogs.microsoft.com/typescript/announcing-typescript-5-6/#iterator-helper-methods