chore(home): drop mutableFiles machinery

The aoe config was the last tracked file, and it drifts the same way
settings.json did. With no consumers left, the module, its repo-path option
and the tracked aoe-config.toml go too.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

home/common/programs/default.nix

@@ -5,7 +5,6 @@
 }:
 {
   imports = [
-    ../features/mutable-file.nix
     ./zsh.nix
     ./nix.nix
     ./neovim
@@ -28,10 +27,6 @@
   };
 
   home = {
-    # mkDefault: hosts whose clone lives elsewhere (yolo, under ~/tea) override
-    # this with a plain assignment.
-    mutableFilesRepoPath = lib.mkDefault "${config.home.homeDirectory}/projects/nixos-config";
-
     username = lib.mkDefault "naps62";
     homeDirectory = lib.mkDefault "/home/${config.home.username}";
     stateVersion = lib.mkDefault "24.05";