devos: devshell: add required pkgs to scope explicitly

the `with pkgs` statement in `commands` muddies the origin of the
variables used within:

- editors are unable to provide helpful advice about undefined variables
  because `with pkgs` acts as a blanket "anything is possible" signifier
- at a cursory glance, it may not be immediately clear that `system` is
  coming from `pkgs.system`
- `lib` is coming from `pkgs.lib`, but we can use the `lib` module arg.
- some pkgs within `commands` are still referenced with
  `pkgs.<package-name>` unnecessarily

devShell.nix

@@ -4,7 +4,7 @@
 let
   pkgs = inputs.nixpkgs.legacyPackages.${system};
   unstablePkgs = inputs.nixpkgs-unstable.legacyPackages.${system};
-  devshell = import inputs.devshell { inherit pkgs system; };
+  devshell = import inputs.devshell { inherit system; };
   nixBin = "${unstablePkgs.nix}/bin/nix";
 
   withCategory = category: attrset: attrset // { inherit category; };

examples/devos/shell/devos.nix

@@ -1,6 +1,17 @@
-{ pkgs, extraModulesPath, inputs, ... }:
+{ pkgs, extraModulesPath, inputs, lib, ... }:
 let
 
+  inherit (pkgs)
+    agenix
+    cachix
+    editorconfig-checker
+    mdbook
+    nixUnstable
+    nixpkgs-fmt
+    nvfetcher-bin
+    system
+    ;
+
   hooks = import ./hooks;
 
   pkgWithCategory = category: package: { inherit package category; };
@@ -30,14 +41,14 @@ in
     unset _PATH
   '');
 
-  commands = with pkgs; [
+  commands = [
     (devos nixUnstable)
     (devos agenix)
     {
       category = "devos";
-      name = pkgs.nvfetcher-bin.pname;
-      help = pkgs.nvfetcher-bin.meta.description;
-      command = "cd $PRJ_ROOT/pkgs; ${pkgs.nvfetcher-bin}/bin/nvfetcher -c ./sources.toml $@";
+      name = nvfetcher-bin.pname;
+      help = nvfetcher-bin.meta.description;
+      command = "cd $PRJ_ROOT/pkgs; ${nvfetcher-bin}/bin/nvfetcher -c ./sources.toml $@";
     }
     (linter nixpkgs-fmt)
     (linter editorconfig-checker)