feat: rework to modular

modules/optional/devtools.nix

@@ -0,0 +1,11 @@
+{ lib, pkgs, ... }:
+let
+  optionalPackage = path: lib.attrByPath path null pkgs;
+in
+{
+  home.packages = builtins.filter (pkg: pkg != null) [
+    (optionalPackage [ "nil" ])
+    (optionalPackage [ "nixd" ])
+    (optionalPackage [ "nixfmt" ])
+  ];
+}

modules/optional/gui.nix

@@ -0,0 +1,9 @@
+{ lib, pkgs, ... }:
+let
+  wezterm = lib.attrByPath [ "wezterm" ] null pkgs;
+in
+{
+  home.packages = builtins.filter (pkg: pkg != null) [
+    wezterm
+  ];
+}

modules/optional/homebrew.nix

@@ -0,0 +1,6 @@
+{ ... }:
+{
+  # Intentionally empty. This is the seam downstream workstations can use to
+  # compose nix-homebrew or Homebrew-specific activation without coupling it
+  # into the shared base roles.
+}