Thin canvas modes, node execution, and canvas draw shell

docs/modernization/roadmap.md

@@ -81,12 +81,12 @@ Current hotspot files:
 
 - `src/canvas.cpp`: 2728 lines
 - `src/app_layout.cpp`: 125 lines
-- `src/canvas_modes.cpp`: 1798 lines
-- `src/node.cpp`: 1465 lines
+- `src/canvas_modes.cpp`: 1710 lines
+- `src/node.cpp`: 1368 lines
 - `src/main.cpp`: 271 lines
 - `src/node_panel_brush.cpp`: 1207 lines
 - `src/node_stroke_preview.cpp`: 910 lines
-- `src/node_canvas.cpp`: 852 lines
+- `src/node_canvas.cpp`: 864 lines
 - `src/app.cpp`: 575 lines
 - `src/app_dialogs.cpp`: 168 lines
 
@@ -240,13 +240,24 @@ Current architecture mismatches that must be treated as real blockers:
   `src/node_stroke_preview.cpp`, while the immediate preview pass-sequencing
   family inside `draw_stroke_immediate()` now also routes through
   `NodeStrokePreview::execute_stroke_draw_immediate_pass_sequence(...)`, while
+  `NodeCanvas::draw()` unmerged-pass blend-gate, layer-orientation, and
+  callback-assembly setup now also route through
+  `execute_node_canvas_draw_unmerged_pass(...)`, which trims another coherent
+  unmerged draw shell from the live node even though the file itself remains
+  large, while shared canvas-mode GL wrappers plus the
+  `CanvasModeBasicCamera` and `CanvasModeCamera` input handlers now also route
+  through `src/legacy_canvas_mode_helpers.*` instead of staying inline in
+  `src/canvas_modes.cpp`, while
   preview stroke preparation, dual-brush setup, and live pass-orchestration
   request assembly now also route through retained preview execution helpers,
   while `Node` child attach/detach/reorder operations now route through named
   local helpers in `src/node.cpp`, and `Node::load_internal(...)` child XML
   loading now also routes through `src/legacy_ui_node_loader.*`, which makes
   the scene-graph mutation and child-instantiation paths easier to reason
-  about without yet reducing the file or moving ownership into `pp_ui_core`,
+  about without yet moving ownership into `pp_ui_core`, while the generic
+  per-frame node execution/traversal family for `restore_context`,
+  `clear_context`, `update`, `update_internal`, and `tick` now also lives in
+  `src/legacy_ui_node_execution.cpp`,
   while `Canvas` point-trace/unproject/project/camera push-pop-get-set and
   face-to-shape helpers now also route through
   `src/legacy_canvas_projection_services.*` instead of staying inline in