Extract final canvas wrappers and preview mix pass

docs/modernization/tasks.md

@@ -36,8 +36,8 @@ Completed, blocked, and superseded task history moved to
   - `pp_legacy_paint_document`: 7 files, about 5709 lines
   - `pp_legacy_app`: 20 files, about 4368 lines
   - `pp_legacy_ui_core`: 20 files, about 3770 lines
-- The biggest single-file choke points are still `src/canvas.cpp`,
-  `src/app_layout.cpp`, `src/canvas_modes.cpp`, `src/node.cpp`,
+- The biggest single-file choke points are still `src/canvas_modes.cpp`,
+  `src/node.cpp`,
   `src/main.cpp`, `src/node_panel_brush.cpp`, `src/node_stroke_preview.cpp`,
   `src/node_canvas.cpp`, `src/app.cpp`, and `src/app_dialogs.cpp`.
 - The platform boundary is not finished:
@@ -90,11 +90,16 @@ looks like a wrapper around the old renderer shell.
 Status: In Progress
 
 Why now:
-`src/canvas.cpp` is still the biggest single architectural blocker at about
-429 lines, with `src/canvas_modes.cpp` now materially thinner and the next
-remaining render-shell pressure shifting toward preview/canvas nodes.
+The live `Canvas` ownership boundary is still active, but `src/canvas.cpp`
+itself is now down to a thin static singleton plus mode-table shell. The
+remaining canvas pressure now sits in the extracted legacy canvas service
+files and the preview/canvas node render paths rather than the old monolithic
+translation unit.
 
 Current slice:
+- The remaining `Canvas` member wrappers in `src/canvas.cpp` now live in the
+  extracted canvas service files, leaving `canvas.cpp` as the static singleton
+  and mode-table shell.
 - Canvas state-management helpers for picking, clear/clear-all, layer
   add/remove/order/lookups, animation frame control, resize, and snapshot
   save/restore now live in `src/legacy_canvas_state_services.cpp` instead of
@@ -213,6 +218,9 @@ Current slice:
   `legacy_node_stroke_preview_execution_services.h`, which trims another
   coherent pass-setup block from `src/node_stroke_preview.cpp`, but broader
   preview-pass orchestration is still inline.
+- `NodeStrokePreview` remaining mix-pass planning and execution now also route
+  through `legacy_node_stroke_preview_draw_services.*`, which trims the last
+  dedicated mix-orchestration pocket from `src/node_stroke_preview.cpp`.
 - `NodeStrokePreview::draw_stroke_immediate()` immediate preview pass
   sequencing now also routes through the private
   `execute_stroke_draw_immediate_pass_sequence(...)` helper, which removes
@@ -1136,6 +1144,10 @@ Current slice:
   `src/node_panel_brush.cpp`, which materially thins another retained preset
   panel UI pocket even though cloud/package worker ownership remains the
   follow-up.
+- `NodePanelBrushPreset` popup-close event handling now also lives in
+  `src/legacy_brush_preset_panel_ui.*` instead of staying inline in
+  `src/node_panel_brush.cpp`, which trims the remaining inline popup tail
+  from the live brush panel file.
 - The retained `LegacyBrushPresetListServices` block now also lives in
   `src/legacy_brush_preset_list_services.*` instead of staying inline in
   `src/node_panel_brush.cpp`, which trims another retained preset workflow