Extract canvas clear command planning

docs/modernization/roadmap.md

@@ -507,6 +507,10 @@ toolbar active-state refresh used by `App::update` before legacy `Canvas` mode
 state remains the source of truth. `NodeCanvas` stylus eraser and `E` key
 draw/erase mode switching also consume the same app-core command planner before
 legacy canvas mode execution continues.
+`pano_cli plan-canvas-clear` exposes app-core planning for the main toolbar
+clear-current-layer command, including clear color validation, no-canvas
+handling, undo recording intent, and dirty-state intent before legacy
+`Canvas::clear` execution continues.
 `pano_cli plan-grid-operation` exposes app-core planning for grid heightmap
 pick/load/reload/clear, lightmap render capability/limit checks, and heightmap
 commit used by the live grid panel before legacy image loading, OpenGL texture
@@ -1180,6 +1184,13 @@ Results:
   `pano_cli_plan_canvas_tool_state_copy_smoke`, and
   `pano_cli_plan_canvas_tool_state_rejects_unknown` passed and expose draw
   toolbar active-state refresh as JSON automation.
+- `pp_app_core_document_canvas_tests` passed, covering clear-current-layer
+  undo/dirty intent, no-canvas no-op behavior, and invalid clear color
+  rejection.
+- `pano_cli_plan_canvas_clear_smoke`,
+  `pano_cli_plan_canvas_clear_no_canvas_smoke`, and
+  `pano_cli_plan_canvas_clear_rejects_bad_color` passed and expose toolbar
+  canvas clear planning as JSON automation.
 - `pp_app_core_history_ui_tests` passed, covering undo/redo availability,
   no-op history commands, clear-history stack/memory state, memory-only clear,
   and negative metric rejection.