chore: disable automatically rearrange windows on macOS

Author: nokazn

hosts/darwin/system.nix

@@ -10,6 +10,8 @@
   dock = {
     orientation = "left";
     autohide = false;
+    # Whether to automatically rearrange spaces based on most recent use. The default is true.
+    mru-spaces = false;
   };
 
   finder = {