Thin recording bridge and canvas draw seams

docs/modernization/roadmap.md

@@ -116,9 +116,10 @@ Current architecture mismatches that must be treated as real blockers:
   sequencing, per-layer/per-plane retained draw execution, and shared
   checkerboard background setup now route through retained draw-merge helpers,
   with the cache-to-screen checkerboard-plane callback setup also reduced and
-  the merged-path per-plane merged-texture draw plus the smoothing-mask face
-  shader/draw pass plus heightmap, current-mode, and grid-mode callback setup
-  now routed through the same retained helper family.
+  the merged-path checkerboard background-plane callback plus per-plane
+  merged-texture draw plus the smoothing-mask face shader/draw pass plus
+  heightmap, current-mode, and grid-mode callback setup now routed through the
+  same retained helper family.
 - `app_layout.cpp` and `app_dialogs.cpp` are still mixed shell/controller files
   rather than thin composition/binding surfaces.
 - `App`, `Canvas`, `Node`, retained workers, and platform entrypoints still use
@@ -138,8 +139,9 @@ Current architecture mismatches that must be treated as real blockers:
   helper instead of a bare static accessor, the prepared-file worker and the
   canvas async import/export/save/open worker now live under `AppRuntime`
   instead of retained static app-events/canvas workers, and `App::rec_loop()`
-  now has a smaller local wait/iteration/encode shell even though the retained
-  recording loop still owns the worker-side readback flow.
+  now delegates worker-iteration orchestration into the retained recording
+  bridge even though that retained recording path still owns the worker-side
+  readback flow.
 - Modern C++23 usage exists in extracted components, especially `std::span`,
   explicit result/status objects, and a few concepts, but the live app still
   does not consistently express ownership, thread affinity, or renderer