Drop ssh module from nikita-nixos host

Add a second nixosConfigurations entry for a friend's machine running
Plasma 6 + SDDM. The hardware-configuration.nix is a placeholder; it
must be replaced with the output of nixos-generate-config on the
actual hardware before installing. Git identity in hosts/nikita-nixos/
home.nix is also a placeholder.

.gitignore

@@ -1 +1,10 @@
 .claude
+docs/
+
+# secret guardrails — keep credentials out of the repo
+secrets/
+*.age
+*.key
+*.pem
+.env
+.env.*

README.md

@@ -0,0 +1,12 @@
+What's verified:
+  - nix flake check passes for both hivebrain and nikita-nixos
+  - nixos-rebuild dry-build --flake .#hivebrain succeeds (your config is unchanged in behavior)
+  - nixos-rebuild dry-build --flake .#nikita-nixos succeeds (Plasma 6 + SDDM derivation resolves)
+  - main is untouched
+
+  What's still TODO before you can install nikita-nixos:
+  - Replace hosts/nikita-nixos/hardware-configuration.nix (placeholder with PLACEHOLDER-ROOT label) with
+  the real output of nixos-generate-config --root /mnt on his machine.
+  - Replace the placeholder git identity in hosts/nikita-nixos/home.nix (currently Nikita /
+  nikita@example.com).
+  - Set Nikita's password with passwd after first boot — nothing is baked in.

configuration.nix

@@ -1,21 +0,0 @@
-{ ... }:
-
-{
-  imports = [
-    ./hardware-configuration.nix
-    ./system/boot.nix
-    ./system/networking.nix
-    ./system/locale.nix
-    ./system/xserver.nix
-    ./system/picom.nix
-    ./system/display-manager.nix
-    ./system/fonts.nix
-    ./system/users.nix
-    ./system/programs.nix
-    ./system/packages.nix
-    ./system/ssh.nix
-    ./system/nix.nix
-  ];
-
-  system.stateVersion = "26.05";
-}

flake.nix

@@ -9,20 +9,32 @@
 		};
 	};
 
-	outputs = { self, nixpkgs, home-manager, ... }: {
-		nixosConfigurations.hivebrain = nixpkgs.lib.nixosSystem {
+	outputs = { self, nixpkgs, home-manager, ... }:
+	let
+		mkHost = { hostPath, username, homePath }: nixpkgs.lib.nixosSystem {
 			system = "x86_64-linux";
 			modules = [
-				./configuration.nix
+				hostPath
 				home-manager.nixosModules.home-manager {
 					home-manager = {
 						useGlobalPkgs = true;
 						useUserPackages = true;
-						users.marvin = import ./home.nix;
+						users.${username} = import homePath;
 						backupFileExtension = "backup";
 					};
 				}
 			];
 		};
+	in {
+		nixosConfigurations.hivebrain = mkHost {
+			hostPath = ./hosts/hivebrain;
+			username = "marvin";
+			homePath = ./hosts/hivebrain/home.nix;
+		};
+		nixosConfigurations.nikita-nixos = mkHost {
+			hostPath = ./hosts/nikita-nixos;
+			username = "nikita";
+			homePath = ./hosts/nikita-nixos/home.nix;
+		};
 	};
 }

home.nix

@@ -1,17 +0,0 @@
-{ ... }:
-
-{
-  imports = [
-    ./home/zsh.nix
-    ./home/git.nix
-    ./home/rofi.nix
-    ./home/yazi.nix
-    ./home/packages.nix
-    ./home/symlinks.nix
-    ./home/fonts.nix
-  ];
-
-  home.username = "marvin";
-  home.homeDirectory = "/home/marvin";
-  home.stateVersion = "26.05";
-}

home/git.nix

@@ -1,11 +0,0 @@
-{ ... }:
-
-{
-  programs.git = {
-    enable = true;
-    settings.user = {
-      name = "MDietermann";
-      email = "marvin.dietermann@hive-brain.de";
-    };
-  };
-}

home/packages-base.nix

@@ -0,0 +1,10 @@
+{ pkgs, ... }:
+
+{
+  home.packages = with pkgs; [
+    neovim
+    nerd-fonts.jetbrains-mono
+    ripgrep
+    unzip
+  ];
+}

home/packages-marvin.nix

@@ -6,17 +6,13 @@
     claude-code
     gcc
     lua-language-server
-    neovim
-    nerd-fonts.jetbrains-mono
     nil
     nixpkgs-fmt
     nodejs
     obsidian
     pkg-config
-    ripgrep
     rustup
     steam
-    unzip
     xwallpaper
   ];
 }

home/zsh.nix

@@ -19,7 +19,7 @@
 
     shellAliases = {
       btw = "echo I use NixOS";
-      reload-nixos = "sudo nixos-rebuild switch --flake ~/nixos-dotfiles#hivebrain";
+      reload-nixos = "sudo nixos-rebuild switch --flake ~/nixos-dotfiles";
     };
   };
 }

hosts/hivebrain/default.nix

@@ -0,0 +1,26 @@
+{ ... }:
+
+{
+  imports = [
+    ./hardware-configuration.nix
+
+    # shared
+    ../../system/boot.nix
+    ../../system/networking.nix
+    ../../system/locale.nix
+    ../../system/fonts.nix
+    ../../system/nix.nix
+    ../../system/ssh.nix
+    ../../system/programs.nix
+    ../../system/packages.nix
+
+    # marvin-only
+    ../../system/xserver.nix
+    ../../system/picom.nix
+    ../../system/display-managers/ly.nix
+    ../../system/users/marvin.nix
+  ];
+
+  networking.hostName = "hivebrain";
+  system.stateVersion = "26.05";
+}

hosts/hivebrain/home.nix

@@ -0,0 +1,25 @@
+{ ... }:
+
+{
+  imports = [
+    ../../home/zsh.nix
+    ../../home/fonts.nix
+    ../../home/rofi.nix
+    ../../home/yazi.nix
+    ../../home/symlinks.nix
+    ../../home/packages-base.nix
+    ../../home/packages-marvin.nix
+  ];
+
+  home.username = "marvin";
+  home.homeDirectory = "/home/marvin";
+  home.stateVersion = "26.05";
+
+  programs.git = {
+    enable = true;
+    settings.user = {
+      name = "MDietermann";
+      email = "marvin.dietermann@hive-brain.de";
+    };
+  };
+}

hosts/nikita-nixos/default.nix

@@ -0,0 +1,24 @@
+{ ... }:
+
+{
+  imports = [
+    ./hardware-configuration.nix
+
+    # shared
+    ../../system/boot.nix
+    ../../system/networking.nix
+    ../../system/locale.nix
+    ../../system/fonts.nix
+    ../../system/nix.nix
+    ../../system/programs.nix
+    ../../system/packages.nix
+
+    # nikita-only
+    ../../system/plasma.nix
+    ../../system/display-managers/sddm.nix
+    ../../system/users/nikita.nix
+  ];
+
+  networking.hostName = "nikita-nixos";
+  system.stateVersion = "26.05";
+}

hosts/nikita-nixos/hardware-configuration.nix

@@ -0,0 +1,24 @@
+{ lib, modulesPath, ... }:
+
+# Placeholder hardware-configuration. Replace with the file generated on
+# Nikita's actual machine via `nixos-generate-config --root /mnt` before
+# building or installing.
+{
+  imports = [
+    (modulesPath + "/installer/scan/not-detected.nix")
+  ];
+
+  boot.initrd.availableKernelModules = [ ];
+  boot.initrd.kernelModules = [ ];
+  boot.kernelModules = [ ];
+  boot.extraModulePackages = [ ];
+
+  fileSystems."/" = {
+    device = "/dev/disk/by-label/PLACEHOLDER-ROOT";
+    fsType = "ext4";
+  };
+
+  swapDevices = [ ];
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+}

hosts/nikita-nixos/home.nix

@@ -0,0 +1,24 @@
+{ ... }:
+
+{
+  imports = [
+    ../../home/zsh.nix
+    ../../home/fonts.nix
+    ../../home/yazi.nix
+    ../../home/symlinks.nix
+    ../../home/packages-base.nix
+  ];
+
+  home.username = "nikita";
+  home.homeDirectory = "/home/nikita";
+  home.stateVersion = "26.05";
+
+  # TODO: replace with Nikita's actual git identity before first use
+  programs.git = {
+    enable = true;
+    settings.user = {
+      name = "Nikita";
+      email = "nikita@example.com";
+    };
+  };
+}

system/display-managers/sddm.nix

@@ -0,0 +1,5 @@
+{ ... }:
+
+{
+  services.displayManager.sddm.enable = true;
+}

system/networking.nix

@@ -1,6 +1,5 @@
 { ... }:
 
 {
-  networking.hostName = "hivebrain";
   networking.networkmanager.enable = true;
 }

system/plasma.nix

@@ -0,0 +1,5 @@
+{ ... }:
+
+{
+  services.desktopManager.plasma6.enable = true;
+}

system/users/nikita.nix

@@ -0,0 +1,12 @@
+{ pkgs, ... }:
+
+{
+  users.users.nikita = {
+    isNormalUser = true;
+    extraGroups = [ "wheel" "networkmanager" ];
+    shell = pkgs.zsh;
+    packages = with pkgs; [
+      tree
+    ];
+  };
+}