weird workflow after deleting `/main` branch.

[aryairani]

llm/main> switch scratch2/

  scratch2/main does not exist.

Oh hm, I guess I deleted it?

llm/main> switch scratch2    

  scratch2/main does not exist.

I'm not sure why I thought this would help

llm/main> branch.create scratch2/main

  Done. I've created the scratch2/main branch based off llm/main.

Ok that's definitely not what I wanted.

scratch2/main> branch.delete scratch2/main
llm/main> 
llm/main> branch.create-empty scratch2/main

  Done. I've created an empty branch scratch2/main.
  
  Tip: Use `merge /somebranch` to initialize this branch.

Ok but it doesn't have base

scratch2/main> lib.install @unison/base

  I installed @unison/base/releases/4.0.0 as unison_base_4_0_0.

Ok great. Though why does this create lib.unison_base_4_0_0 while project.create creates lib.base?

[ceedubs]

Related: #4181