chore: dev workflow with remix watch

[hi-ogawa]

cf. https://github.com/remix-run/remix/blob/ea7ab3adf1cc38a3ee40261f8d40d9b2535455ba/templates/express/package.json#L7-L8

We won't need globalThis server state hack anymore.
Also, it might be interesting to implement hattip-based handler directly from server-runtime, then we can borrow all the adapters from https://github.com/hattipjs/hattip/tree/main/packages/adapter.
Then also we might be able to do more elegant things for

• chore: replace deprecated vercel entrypoint #337