zen: unsandbox autoconfig so the theme watcher can run

Firefox 62+ restricts mozilla.cfg to pref()/defaultPref(); Components was
undefined, so the watcher threw on its first line and so did its catch.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/zen.nix

@@ -17,9 +17,13 @@ let
   # BEFORE the profile's userChrome.css, which would let the startup copy
   # outrank every sheet we register.
   #
-  # Everything here goes through Components.classes. The autoconfig sandbox is
-  # not a normal system-principal scope: `Services` is not a global in it, and
-  # reaching for it throws before a single sheet is registered.
+  # Everything here goes through Components.classes rather than `Services`,
+  # which is not a global in this scope.
+  #
+  # None of it runs without general.config.sandbox_enabled=false below: since
+  # Firefox 62 autoconfig is sandboxed down to pref()/defaultPref(), so
+  # `Components` is undefined and the script throws on its first line — as does
+  # the catch that would have reported it.
   #
   # Diagnosing a silent failure: about:config -> fred.zenTheme.status holds
   # "ok <mtime>", "missing <path>" or "error <exception>" from the last pass.
@@ -90,6 +94,9 @@ in
   config = lib.mkIf (lib.elem config.networking.hostName [ "FredOS-Gaming" "FredOS-Macbook" ]) {
     environment.systemPackages = [
       (inputs.zen-browser.packages.${pkgs.stdenv.hostPlatform.system}.default.override {
+        # Lands in defaults/pref/autoconfig.js, the only place this pref is
+        # read — setting it from mozilla.cfg is too late to unsandbox itself.
+        extraAutoConfig = ''pref("general.config.sandbox_enabled", false);'';
         extraPrefs = themeHotReload;
       })
     ];