Extract draw toolbar and thin NodeCanvas and Win32 shell

docs/modernization/tasks.md

@@ -225,6 +225,11 @@ Current slice:
   `execute_legacy_canvas_draw_unmerged_shell(...)`, which removes another
   coherent orchestration block from `NodeCanvas::draw()` even though the
   broader node draw loop still lives in `src/node_canvas.cpp`.
+- `NodeCanvas` unmerged-path onion-range planning, plane filtering, per-layer
+  visit handling, and per-visit layer-path execution now also route through
+  `execute_legacy_canvas_draw_unmerged_node_canvas_shell(...)`, which trims
+  another outer draw-shell block even though the broader node draw loop still
+  lives in `src/node_canvas.cpp`.
 
 Write scope:
 - `src/node_stroke_preview.cpp`
@@ -303,7 +308,7 @@ targets look like helpers under one old monolith.
 Status: In Progress
 
 Why now:
-`src/app_layout.cpp` is still a 353-line mixed file that builds menus,
+`src/app_layout.cpp` is still a 285-line mixed file that builds menus,
 attaches callbacks, computes planner inputs, and mutates UI state directly.
 
 Current slice:
@@ -333,6 +338,9 @@ Current slice:
 - UI-direction plus persisted floating/docked panel-state ownership now also
   lives in `src/app_layout_ui_state.cpp`, and `src/app_layout.cpp` is down to
   the remaining draw-toolbar, brush-refresh, and layout/bootstrap composition.
+- Draw-toolbar binding now also lives in `src/app_layout_draw_toolbar.cpp`, and
+  `src/app_layout.cpp` is down to the remaining brush-refresh and
+  layout/bootstrap composition.
 
 Write scope:
 - `src/app_layout.cpp`
@@ -498,6 +506,9 @@ Current slice:
   discovery, startup-state initialization, window creation, pixel-format
   setup, GL loader init, runtime-info logging, and core-context upgrade
   sequencing
+- BugTrap/SEH recovery setup now also lives in
+  `src/platform_windows/windows_bootstrap_helpers.cpp` instead of
+  `src/main.cpp`
 - the Win32 window procedure and retained message-handling shell now also live
   in `src/platform_windows/windows_window_shell.*` instead of `src/main.cpp`,
   which materially thins the entry file even though broader runtime/entrypoint