fix: create greeter home for tuigreet remember and document NVMe model

Co-authored-by: aider (openrouter/openai/gpt-5.2) <aider@aider.chat>

docs/nixos_build_spec.md

@@ -2,6 +2,7 @@
 
 ## Disk / Boot (DO NOT BRICK WINDOWS)
 Target disk: /dev/nvme0n1
+- Model: PM951 NVMe SAMSUNG 1024GB
 - Sector size (logical/physical): 512 bytes / 512 bytes
 Install target is NVMe only. Do not select /dev/sdX devices in the installer.
 

hosts/sam-4screen-desktop/configuration.nix

@@ -71,6 +71,8 @@
   users.users.greeter = {
     isSystemUser = true;
     group = "greeter";
+    home = "/var/lib/greeter";
+    createHome = true;
   };
 
   # ---