fix(storybook-builder-parcel): hoist runtime import, use public preview-api path
Move `import { setup } from 'storybook/internal/preview/runtime'` to be the
first import in the generated preview-main.js so runtime.js's top-level setup()
call populates __STORYBOOK_MODULE_* globals before setup-addons.js (or any other
externalized specifier) evaluates and tries to destructure those globals.
Also switch `from 'storybook/internal/preview-api'` to the public
`from 'storybook/preview-api'` to match the externalize map and upstream
Vite/webpack5 ordering.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>