`@remotion/studio`: Restore CJS worker mirror to fix visual controls

Reverts the ESM aliasing of `@remotion/studio` and `@remotion/studio/previewEntry` because the bundled ESM entries duplicate the visual-control singleton and break the Controls panel. Reintroduces the post-build copy of the waveform worker so CJS consumers can still resolve `./audio-waveform-worker.mjs` next to the helper.