[SiriusA] Adds configuration. [MCP] Cleans up config file.

flake.nix

@@ -59,6 +59,9 @@
         mcp = mkNixosConfig {
           path = ./system/hosts/mcp;
         };
+        sirius-a = mkNixosConfig {
+          path = ./system/hosts/sirius-a;
+        };
       };
       features = {
         development = import ./home-manager/features/development/development.nix;