Avoid host mutation for early cache hints

README.md

@@ -26,20 +26,18 @@ the AMI:
 ```nix
 {
   quixosEarlyBuildNixConfig = {
-    hosts = {
-      "2600:..." = [ "nix-cache.internal.example.org" ];
-    };
-    substituters = [ "http://nix-cache.internal.example.org/cache" ];
+    substituters = [ "http://[2600:...]/cache" ];
     trustedPublicKeys = [ "nix-cache.internal.example.org-1:..." ];
   };
 }
 ```
 
-The AMI runner evaluates this output after writing `/etc/nixos/flake.nix`,
-appends the host hints to `/etc/hosts`, and passes the substituters and trusted
-public keys through `NIX_CONFIG` only for the first `nixos-rebuild switch`.
-The target NixOS configuration should still declare the same cache in
-`nix.settings` for all later rebuilds.
+The AMI runner evaluates this output after writing `/etc/nixos/flake.nix` and
+passes the substituters and trusted public keys through `NIX_CONFIG` only for
+the first `nixos-rebuild switch`. It does not mutate `/etc/hosts`; first-boot
+substituters that need private addressing should use a direct address URL. The
+target NixOS configuration should still declare the normal hostname-based cache
+in `nix.settings` and `networking.hosts` for all later rebuilds.
 
 ## Publish