Extract layout bootstrap and thin NodeCanvas startup shells

docs/modernization/roadmap.md

@@ -80,13 +80,13 @@ What is still carrying too much live ownership:
 Current hotspot files:
 
 - `src/canvas.cpp`: 2645 lines
-- `src/app_layout.cpp`: 229 lines
+- `src/app_layout.cpp`: 125 lines
 - `src/canvas_modes.cpp`: 1798 lines
 - `src/node.cpp`: 1594 lines
-- `src/main.cpp`: 390 lines
+- `src/main.cpp`: 271 lines
 - `src/node_panel_brush.cpp`: 1197 lines
 - `src/node_stroke_preview.cpp`: 890 lines
-- `src/node_canvas.cpp`: 831 lines
+- `src/node_canvas.cpp`: 852 lines
 - `src/app.cpp`: 502 lines
 - `src/app_dialogs.cpp`: 142 lines
 
@@ -135,7 +135,14 @@ Current architecture mismatches that must be treated as real blockers:
   `execute_legacy_canvas_draw_unmerged_node_canvas_shell(...)`, while the
   broader unmerged cache/viewport/background/composite pass setup now also
   routes through
-  `execute_legacy_canvas_draw_unmerged_node_canvas_pass(...)`.
+  `execute_legacy_canvas_draw_unmerged_node_canvas_pass(...)`, while
+  `NodeCanvas::draw()` setup, merged-pass shell, and unmerged-pass shell now
+  also route through `prepare_legacy_node_canvas_draw_setup(...)`,
+  `execute_legacy_canvas_draw_node_canvas_shell(...)`,
+  `execute_legacy_canvas_draw_merged_pass(...)`, and
+  `execute_legacy_canvas_draw_node_canvas_unmerged_pass(...)`, which
+  materially shortens the live `NodeCanvas::draw()` body even though the file
+  itself is still large.
 - `app_layout.cpp` and `app_dialogs.cpp` are still mixed shell/controller files
   rather than thin composition/binding surfaces, even though tools-menu binding
   plus nested panels/options submenu wiring now live in
@@ -154,8 +161,9 @@ Current architecture mismatches that must be treated as real blockers:
   persisted floating/docked panel-state ownership now also live in
   `src/app_layout_ui_state.cpp`, while draw-toolbar binding now also lives in
   `src/app_layout_draw_toolbar.cpp`, while brush-refresh now also lives in
-  `src/app_layout_brush.cpp`, and `src/app_layout.cpp` is now mostly
-  layout/bootstrap composition, while the
+  `src/app_layout_brush.cpp`, while layout bootstrap plus reload/load
+  continuation wiring now also lives in `src/app_layout_bootstrap.cpp`, and
+  `src/app_layout.cpp` is now mostly thin call-through entrypoints, while the
   informational overlay opener family now also lives in
   `src/app_dialogs_info_openers.cpp` and the corresponding `App::dialog_*`
   entrypoints are thinner, while the export/video/PPBR dialog family now also
@@ -193,8 +201,9 @@ Current architecture mismatches that must be treated as real blockers:
   while the retained Win32 VR/HMD shell now also routes through
   `src/platform_windows/windows_vr_shell.h` instead of staying inline in
   `src/main.cpp`, while RenderDoc startup/frame capture, SHCore DPI bootstrap,
-  Win32 error-string conversion, and the GL debug pre/post callbacks now also
-  live in `src/platform_windows/windows_bootstrap_helpers.cpp` instead of
+  Win32 error-string conversion, the GL debug pre/post callbacks, and the WMI
+  startup probe now also live in
+  `src/platform_windows/windows_bootstrap_helpers.cpp` instead of
   `src/main.cpp`, while Win32 lifecycle running-state, close/shutdown
   sequencing, FPS title update/wakeup posting, stylus frame update, window
   preference save, and VR lifecycle wrappers now also live in