Fix aerospace namespace conflict and claude-code override

Rename custom aerospace module from services.aerospace to roles.aerospace
to avoid conflicting with nix-darwin's built-in aerospace service support.

Move claude-code package override to flake-level overlay to ensure the
GCS-distributed version is used instead of the npm registry version in
unstable. This is necessary for corporate environments where npm registry
access may be blocked.

machines/johno-macbookpro/configuration.nix

@@ -18,10 +18,11 @@
     NSGlobalDomain.AppleShowAllExtensions = true;
   };
 
-  # Enable aerospace system settings
-  services.aerospace = {
+  # Enable our custom aerospace system configuration
+  # (separate from nix-darwin's services.aerospace which manages the service)
+  roles.aerospace = {
     enable = true;
-    enableSpansDisplays = true;  # Default, but shown for clarity
+    enableSpansDisplays = true;
   };
 
   # TODO: Find a way to not duplicate this