Rebuilt JS assets in production mode

The committed `assets/built/index.js` was produced by the development
build (`rollup --environment BUILD:development`): it began with the
livereload script-injection snippet, which every site using the Starter
theme shipped to visitors — attempting to load a livereload server from
the visiting host on port 35729. Rebuilt with `pnpm build` (production
mode), which drops the livereload plugin and bundles only the theme
code. Verified the rebuild is deterministic and gscan reports no errors
(4 pre-existing warnings unrelated to this change).

Found while fixing the pnpm action pin (#133).

Author: aileen