Centralize retained dialog cancel bindings

docs/modernization/roadmap.md

@@ -500,6 +500,8 @@ About, changelog, settings, and user-manual close buttons now share retained
 destroy-on-click binding through the same overlay service.
 Message-box submit/cancel and input-box cancel destroy callbacks now use the
 same retained close binding helpers.
+Document open/save/new/browse/resize, layer-rename, cloud-browse, and PPBR
+export dialog cancel buttons now use those same retained close helpers.
 Raw popup callback captures and full close/capture ownership remain part of
 `DEBT-0063`.
 `pano_cli inspect-image` exposes PNG IHDR metadata as JSON,