* feat(scripts): typecheck the scripts directory
scripts/ was the one TypeScript surface nothing typechecked. Adding a project for it surfaced real errors rather than style: a preview generator passing string | undefined where a string was required, a readdir result indexed without a bound, and two non-null assertions standing in for a filter that could have narrowed the type instead.
The two preview generators had also drifted into sharing a capture setup, down to the comment explaining why the capture is opaque. That lifts into scripts/preview-capture.ts, so the reason is written once and both callers own the handles they have to close.
@hyperframes/core and @hyperframes/producer become dev dependencies because the scripts import them; without that the project resolves on a machine with a warm node_modules and fails in CI.
* fix(scripts): use source imports consistently
