home-manager: enable for darman on every host, not just terra

terra was the only host with real ~/.zshrc/.zshenv (via home-manager),
so it never hit the plain-zsh zsh-newuser-install wizard that shows up
on first login everywhere else. Wire home-manager.nixosModules.home-manager
into jupiter/neptun/mars/mercury (+ mercury-vm/jupiter-vbox test targets)
and give darman terra's shared zsh baseline via home/common.nix, imported
from common.nix. terra's own home.nix now only carries its
desktop/dev-specific profile (Hyprland, alacritty, git identity, direnv,
dev packages) layered on top via home-manager.users.darman.imports.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Du1WQRk1F8DenrPhf8TofF

hosts/terra/configuration.nix

@@ -43,11 +43,12 @@ in
   programs.nix-ld.enable = true;
 
   # ---- home-manager (user-level config for darman) ----
-  home-manager.useGlobalPkgs = true;
-  home-manager.useUserPackages = true;
-  home-manager.backupFileExtension = "hm-bak";
+  # Base settings (useGlobalPkgs/useUserPackages/backupFileExtension) and the
+  # shared zsh baseline now live in common.nix + home/common.nix, applied to
+  # every host. This just layers terra's desktop/dev-specific profile on top
+  # — home-manager.users.darman.imports merges additively across modules.
   home-manager.extraSpecialArgs = { inherit unstable inputs; };
-  home-manager.users.darman = import ./home.nix;
+  home-manager.users.darman.imports = [ ./home.nix ];
 
   # ---- Boot (UEFI) ----
   boot.loader.systemd-boot.enable = true;

hosts/terra/home.nix

@@ -3,9 +3,11 @@ let
   tome = pkgs.callPackage ../../pkgs/tome.nix { src = inputs.tome; };
 in
 {
+  # home.stateVersion, programs.home-manager.enable, programs.zsh.enable all
+  # come from home/common.nix (shared across every host) via
+  # configuration.nix's home-manager.users.darman.imports.
   imports = [ ./home/hyprland.nix ./home/theme.nix ];
 
-  home.stateVersion = "26.05";
   home.keyboard.layout = "de";
 
   programs.git = {
@@ -15,9 +17,6 @@ in
       user.email = "mail@erik-s.dev";
     };
   };
-  programs.home-manager.enable = true;
-
-  programs.zsh.enable = true;
 
   # direnv + nix-direnv: lets per-repo devShells (e.g. ~/Data/Dev/repos/Tome's
   # flake.nix) auto-load in the shell AND in Rider via its "direnv