fix: Generated types no longer permanently delete themselves

[elliott-with-the-longest-name-on-github]

Fixes #5059.

svelte-kit sync always completely deletes the types directory when it writes types. Then, it re-writes types by looking for changed files. If no files have been changed, the types directory is gone for good (or at least until a file is changed). See the repro in the linked issue.

This fixes the issue by always rewriting all of the types (since we're deleting everything, we need to rewrite everything). I'm not really sure how to test this change, though this does fix the repro.

If there's some larger issue here that needs a bigger fix, feel free to just close this and move on!

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Latest commit: 8a351a4

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[Rich-Harris]

thank you!