feat: add build timestamp service and version info to bash init

common.nix

@@ -335,6 +335,20 @@ isoConfig
      };
    };
 
+   # Build timestamp service
+   systemd.services.workshop-build-info = {
+     description = "Write build timestamp to /etc/workshop-build-info";
+     wantedBy = [ "multi-user.target" ];
+     script = ''
+       echo "$(date '+%Y-%m-%d %H:%M:%S')" > /etc/workshop-build-info
+     '';
+     serviceConfig = {
+       Type = "oneshot";
+       User = "root";
+       RemainAfterExit = true;
+     };
+   };
+
    services.getty.autologinUser = "workshop";
   security.sudo.wheelNeedsPassword = false;
 
@@ -584,6 +598,9 @@ isoConfig
              echo "⚠️ abra not found! Check: systemctl status workshop-abra-install"
            fi
 
+           # Build info
+           echo "✅ Workshop ISO - NixOS $(nixos-version) - Built: $(cat /etc/workshop-build-info 2>/dev/null || echo 'unknown')"
+
           # Bash Completion Configuration
           _workshop_completion() {
             local cur prev