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/features/mutable-file.nix

@@ -1,105 +0,0 @@
-{
-  config,
-  lib,
-  pkgs,
-  self,
-  ...
-}:
-let
-  cfg = config.home.mutableFiles;
-  repoPath = config.home.mutableFilesRepoPath;
-  flakePrefix = self.outPath;
-
-  fileEntries = lib.attrsToList cfg;
-
-  toRepoPath = storePath: repoPath + lib.removePrefix flakePrefix (toString storePath);
-
-  checkScript = lib.concatMapStringsSep "\n" (
-    { name, value }:
-    let
-      target = "${config.home.homeDirectory}/${name}";
-      storePath = value.source;
-      # toRepoPath only works for sources that live in the flake tree. A
-      # generated source is not under flakePrefix, so removePrefix is a no-op
-      # and the hint would print a /nix/store path to copy back onto.
-      originalPath =
-        if value.upstreamPath != null then "${repoPath}/${value.upstreamPath}" else toRepoPath value.source;
-    in
-    ''
-      if [ -f "${target}" ] && ! ${lib.getExe' pkgs.diffutils "diff"} -q "${storePath}" "${target}" > /dev/null 2>&1; then
-        echo ""
-        echo "!! mutable file changed: ${name}"
-        echo "   To bring changes upstream:"
-        echo "   cp ${target} ${originalPath}"
-        echo ""
-        ${lib.getExe' pkgs.diffutils "diff"} -u "${storePath}" "${target}" || true
-        _mutable_changed=1
-      fi
-    ''
-  ) fileEntries;
-
-  copyScript = lib.concatMapStringsSep "\n" (
-    { name, value }:
-    let
-      target = "${config.home.homeDirectory}/${name}";
-      inherit (value) source;
-      dirName = builtins.dirOf target;
-    in
-    ''
-      mkdir -p "${dirName}"
-      cp -f "${source}" "${target}"
-      chmod ${if value.executable then "755" else "644"} "${target}"
-    ''
-  ) fileEntries;
-in
-{
-  options.home.mutableFilesRepoPath = lib.mkOption {
-    type = lib.types.str;
-    description = "Absolute path to the nixos-config repo on disk.";
-  };
-
-  options.home.mutableFiles = lib.mkOption {
-    type = lib.types.attrsOf (
-      lib.types.submodule {
-        options = {
-          source = lib.mkOption {
-            type = lib.types.path;
-            description = "Path to the source file.";
-          };
-          executable = lib.mkOption {
-            type = lib.types.bool;
-            default = false;
-            description = "Whether the file should be executable.";
-          };
-
-          upstreamPath = lib.mkOption {
-            type = lib.types.nullOr lib.types.str;
-            default = null;
-            example = "home/yolo/aoe-config.toml";
-            description = ''
-              Repo-relative file to name in the "bring changes upstream" hint.
-              Required when `source` is generated rather than a file in the
-              flake tree, since the store path cannot be mapped back.
-            '';
-          };
-        };
-      }
-    );
-    default = { };
-    description = "Files to copy (not symlink) into the home directory, with change detection.";
-  };
-
-  config = lib.mkIf (cfg != { }) {
-    home.activation.mutableFiles = lib.hm.dag.entryAfter [ "writeBoundary" ] ''
-      _mutable_changed=0
-      ${checkScript}
-      if [ "$_mutable_changed" -eq 1 ]; then
-        echo ""
-        echo "!! Aborting: mutable files have been modified outside of nix."
-        echo "   Bring the changes upstream first, then re-run."
-        exit 1
-      fi
-      ${copyScript}
-    '';
-  };
-}

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";