Handle build errors on `edgespec dev`

[codetheweb]

Yes, the headless coupling layer has once again been refactored. I promise this is the final time.

Previously we effectively had an RPC-style system but without actually formalizing it as such. We now use birpc as a very simple RPC provider. This allows us to offload the mutex/race condition logic to the bundler instead of the HTTP server and greatly simplifies the flow.

But wait, there's more.

Build errors no longer cause the process to crash:

before:

https://github.com/seamapi/edgespec/assets/7410405/27f3a311-f6bf-4e74-a964-38edf3476a56

after:

https://github.com/seamapi/edgespec/assets/7410405/90f6b169-4610-4abe-9a55-82480876fee6

[codetheweb]

the flaky test seems to have also been fixed by this 🎉