refactor: fully rebase to nixpkgs-unstable rather than fixed release with backports

hosts/franks-macbook-pro/configuration.nix

@@ -1,11 +1,7 @@
 {
   pkgs,
-  inputs,
   ...
 }:
-let
-  unstable = inputs.nixpkgs-unstable.legacyPackages.${pkgs.stdenv.hostPlatform.system};
-in
 {
   imports = [
     ../shared/darwin.nix
@@ -15,8 +11,7 @@ in
     systemPackages = with pkgs; [
       bash-language-server
       nil
-
-      unstable.devenv
+      devenv
     ];
 
     shellAliases = {
@@ -25,7 +20,6 @@ in
   };
 
   homebrew.casks = [
-    "zed"
     "firefox"
   ];