Extract canvas projection helpers and thin preview and node loading

docs/modernization/roadmap.md

@@ -79,16 +79,16 @@ What is still carrying too much live ownership:
 
 Current hotspot files:
 
-- `src/canvas.cpp`: 2645 lines
+- `src/canvas.cpp`: 2728 lines
 - `src/app_layout.cpp`: 125 lines
 - `src/canvas_modes.cpp`: 1798 lines
-- `src/node.cpp`: 1594 lines
+- `src/node.cpp`: 1465 lines
 - `src/main.cpp`: 271 lines
-- `src/node_panel_brush.cpp`: 1197 lines
-- `src/node_stroke_preview.cpp`: 890 lines
+- `src/node_panel_brush.cpp`: 1207 lines
+- `src/node_stroke_preview.cpp`: 910 lines
 - `src/node_canvas.cpp`: 852 lines
-- `src/app.cpp`: 502 lines
-- `src/app_dialogs.cpp`: 142 lines
+- `src/app.cpp`: 575 lines
+- `src/app_dialogs.cpp`: 168 lines
 
 Current architecture mismatches that must be treated as real blockers:
 
@@ -240,10 +240,17 @@ 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
-  `Node` child attach/detach/reorder operations now route through named local
-  helpers in `src/node.cpp`, which makes the scene-graph mutation paths easier
-  to reason about without yet reducing the file or moving ownership into
-  `pp_ui_core`.
+  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`,
+  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
+  `src/canvas.cpp`.
 - 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