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

common.nix

@@ -53,6 +53,19 @@
 
   environment.systemPackages = with pkgs; [ git btop tmux curl wget zsh-powerlevel10k lsd ];
 
+  # ---- home-manager (user-level config for darman, all hosts) ----
+  # Requires home-manager.nixosModules.home-manager in the host's own
+  # `modules` list (flake.nix) — this only sets values for options that
+  # module declares, it doesn't import it, so every nixosSystem using
+  # common.nix needs that line too (mirrors terra's original setup).
+  home-manager.useGlobalPkgs = true;
+  home-manager.useUserPackages = true;
+  # Protects activation if a plain (non-symlink) ~/.zshrc etc. already
+  # exists from before home-manager managed it — e.g. a host where the
+  # zsh-newuser-install wizard's option (0) was used to silence itself.
+  home-manager.backupFileExtension = "hm-bak";
+  home-manager.users.darman.imports = [ ./home/common.nix ];
+
   # ---- zsh / oh-my-zsh / powerlevel10k ----
   programs.zsh = {
     enable = true;

flake.nix

@@ -80,6 +80,7 @@
           modules = [
             disko.nixosModules.disko
             sops-nix.nixosModules.sops
+            home-manager.nixosModules.home-manager
             ./hosts/jupiter/configuration.nix
           ];
         };
@@ -91,6 +92,7 @@
           modules = [
             disko.nixosModules.disko
             sops-nix.nixosModules.sops
+            home-manager.nixosModules.home-manager
             ./hosts/neptun/configuration.nix
           ];
         };
@@ -117,6 +119,7 @@
           modules = [
             disko.nixosModules.disko
             sops-nix.nixosModules.sops
+            home-manager.nixosModules.home-manager
             ./hosts/mars/configuration.nix
           ];
         };
@@ -131,6 +134,7 @@
           modules = [
             (nixpkgs + "/nixos/modules/installer/sd-card/sd-image-aarch64.nix")
             sops-nix.nixosModules.sops
+            home-manager.nixosModules.home-manager
             ./hosts/mercury/configuration.nix
           ];
         };
@@ -143,6 +147,7 @@
           inherit system;   # x86_64-linux, fast to build/boot with KVM
           modules = [
             (nixpkgs + "/nixos/modules/virtualisation/qemu-vm.nix")
+            home-manager.nixosModules.home-manager
             ./common.nix
             ./services/network/unbound.nix
             ./services/network/pihole.nix
@@ -169,7 +174,10 @@
         jupiter-vbox = nixpkgs.lib.nixosSystem {
           inherit system;
           specialArgs = { inherit inputs; };
-          modules = [ ./hosts/jupiter/vm.nix ];
+          modules = [
+            home-manager.nixosModules.home-manager
+            ./hosts/jupiter/vm.nix
+          ];
         };
 
         # Custom kexec installer with our SSH key baked in, for headless install

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