Require ResolveBackendInEnv to deny stub (and empty stub fallback) when
env is main/prod so production cannot request simulated agent output.
Co-authored-by: Cursor <cursoragent@cursor.com>
CAS the unique terminal status with the assistant turn, frozen manifest, envelope and FAV staging, and join ctxmgr writes through the same UoW instead of a process mutex.
Co-authored-by: Cursor <cursoragent@cursor.com>