Vouch request: envvars.update ReferenceError (#4264) #4901

I'd like to land a fix for #4264. Ran tsx --eval with update("proj_x","dev","FOO",{value:"bar"}) on 0a23814 against packages/trigger-sdk/src/v3/envvars.ts. It threw ReferenceError: name is not defined at line 341. Branch is fix/4264-envvars-update-name with the assignment and a regression test.

First PR here. Fork is claxman/trigger.dev.