This repo has two projects: core (a vanilla TS project) and cf (a Cloudflare Worker that depends on core).
You can develop on the cf project by running npm run dev in the cf directory.
If you want to develop on the core project and automatically rebuild the cf project then run npm dev in a separate process in the core project.
command prompt 1
cd core
npm i
npm run dev
command prompt 2
cd cf
npm i
npm run dev