Extract dialog, VR, and canvas draw helpers

docs/modernization/tasks.md

@@ -195,8 +195,11 @@ Current slice:
   broader draw-loop and renderer-state shell sequencing.
 - `NodeCanvas` outer non-`draw_merged` layer/plane traversal, onion-range
   failure handling, and visit payload setup now also route through
-  `execute_legacy_canvas_draw_layer_traversal(...)`, but the node still owns
-  the heavier per-layer GL setup and draw lambdas.
+  `execute_legacy_canvas_draw_layer_traversal(...)`.
+- `NodeCanvas` non-`draw_merged` per-layer temporary erase/paint, layer-texture,
+  and blend setup now also route through
+  `make_legacy_canvas_draw_merge_layer_path_gl_execution(...)`, but the node
+  still owns the remaining draw lambdas and broader renderer-state shell.
 
 Write scope:
 - `src/node_stroke_preview.cpp`
@@ -325,6 +328,13 @@ Why now:
 `src/app_dialogs.cpp` still mixes document workflow decisions, export routing,
 dialog construction, and overlay ownership.
 
+Current slice:
+- Informational overlay opener paths for user manual, changelog, about,
+  what's-new, and shortcuts now live in `src/app_dialogs_info_openers.cpp`,
+  and the corresponding `App::dialog_*` entrypoints are now thin call-throughs,
+  but document/export workflow and retained dialog execution are still inline in
+  `src/app_dialogs.cpp`.
+
 Write scope:
 - `src/app_dialogs.cpp`
 - `src/legacy_app_dialog_services.*`
@@ -417,6 +427,10 @@ Current slice:
   reset, and `WM_POINTERUPDATE` pen/touch handling now live in
   `src/platform_windows/windows_stylus_input.cpp` instead of `src/main.cpp`,
   but broader retained Win32 shell state is still open
+- the retained Win32 VR/HMD shell, including worker start/stop and VR FPS
+  state, now routes through `src/platform_windows/windows_vr_shell.h` instead
+  of staying inline in `src/main.cpp`, but broader retained Win32 shell state
+  is still open
 - prepared-file background work now runs through an `AppRuntime`-owned worker
   queue instead of a retained static worker in `src/app_events.cpp`
 - canvas async import/export/save/open background work now also runs through an