- dmd current nixpkgs and overlay identical

- nixDirEnv (a copy of .envrc) used for flake.nix
  (getting around an issue that arose when
  building project; may revert to direct use of
  .envrc)

- strange events yesterday, I am assuming that this substitution is a
  long past uncommited change (as the like was needed and considered);
  rather than the demonstration of my having being hacked, which if it
  was, appears to have been rather kindly done considering the
  implications of such access (seemingly having left everything else
  untouched, though it implies access to and considerable knowledge of
  this code base), and the choice of poem, one that I might make but
  would be generous for someone else to choose for me.