Fix assertion on nixos-unstable

Failed assertions:
- 25.05.20250309.e3e32b6 is an invalid value for 'system.stateVersion'; it must be in the format "YY.MM",
which corresponds to a prior release of NixOS.

Author: SuperSandro2000

examples/graphics.nix

@@ -22,7 +22,7 @@ nixpkgs.lib.nixosSystem {
       };
 
       networking.hostName = "graphical-microvm";
-      system.stateVersion = config.system.nixos.version;
+      system.stateVersion = lib.trivial.release;
       nixpkgs.overlays = [ self.overlay ];
 
       services.getty.autologinUser = "user";

examples/microvms-host.nix

@@ -35,7 +35,7 @@ nixpkgs.lib.nixosSystem {
 
       in {
         networking.hostName = "microvms-host";
-        system.stateVersion = config.system.nixos.version;
+        system.stateVersion = lib.trivial.release;
         users.users.root.password = "";
         users.motd = ''
           Once nested MicroVMs have booted you can look up DHCP leases:
@@ -66,7 +66,7 @@ nixpkgs.lib.nixosSystem {
         # Nested MicroVMs (a *host* option)
         microvm.vms = builtins.mapAttrs (hypervisor: mac: {
           config = {
-            system.stateVersion = config.system.nixos.version;
+            system.stateVersion = lib.trivial.release;
             networking.hostName = "${hypervisor}-microvm";
 
             microvm = {

examples/qemu-vnc.nix

@@ -28,7 +28,7 @@ nixpkgs.lib.nixosSystem {
       };
 
       networking.hostName = "qemu-vnc";
-      system.stateVersion = config.system.nixos.version;
+      system.stateVersion = lib.trivial.release;
 
       microvm.qemu.extraArgs = [
         "-vnc" ":0"

flake.nix

@@ -181,7 +181,7 @@
                 modules = [
                   self.nixosModules.microvm
                   ({ config, lib, ... }: {
-                    system.stateVersion = config.system.nixos.version;
+                    system.stateVersion = lib.trivial.release;
 
                     networking.hostName = "${hypervisor}-microvm";
                     services.getty.autologinUser = "root";