fix: strip typescript assertions before analysis

[gtm-nayan]

Svelte 5 rewrite

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[dummdidumm]

Looks promising! In the transformation phase there's a TS visitor (I think in typescript.js) which removes type-related constructs, I think this could be moved into this pre-visitor.

[gtm-nayan]

yeah probably, will get to that in the evening

[Rich-Harris]

nice!