Refactor desktop HM into desktop-home-base and per-host home.nix

modules/desktop/shells/dms/home-manager/default.nix

@@ -123,7 +123,7 @@ in {
     {
 
   # Nix rebuild widget used by DankMaterialShell (via nix-monitor).
-  # Per-host `rebuildCommand` is set in `hosts/clients/<host>/home.nix`.
+  # Per-host `rebuildCommand` is set in `modules/hosts/<host>/configuration.nix` (`chiasson.desktop.shells.dms`).
   programs.nix-monitor = {
     enable = true;
     generationsCommand = [
@@ -1108,6 +1108,12 @@ in {
   '';
   }
   (lib.mkIf (lib.attrByPath [ "chiasson" "home" "shell" "ohMyPosh" "enable" ] false config) {
+    # Matugen overwrites this at runtime; seed a stock theme so `oh-my-posh init fish` works before DMS runs matugen.
+    xdg.configFile."oh-my-posh/theme.omp.json".source =
+      let
+        ompTheme = config.chiasson.home.shell.ohMyPosh.builtinTheme or "jandedobbeleer";
+      in
+      "${config.programs.oh-my-posh.package}/themes/${ompTheme}.omp.json";
     # Same path as matugen `[templates.ohmyposh]` output in `programs.dank-material-shell` config.
     programs.oh-my-posh = {
       useTheme = lib.mkForce null;