steal some nix options from jackson.dev

https://jackson.dev/post/nix-reasonable-defaults/

hosts/common/core/nix.nix

@@ -20,6 +20,10 @@
             keep-outputs = true;
             keep-derivations = true;
             use-xdg-base-directories = true;
+            connect-timeout = 5;
+            log-lines = 25;
+            fallback = true;
+            warn-dirty = false;
         };
     };
 }