Add brush UI service boundary

docs/modernization/roadmap.md

@@ -503,7 +503,8 @@ before legacy `Canvas`/`Layer` frame execution continues.
 `pano_cli plan-brush-operation` exposes app-core planning for brush color
 changes, tip/pattern/dual texture changes, preset brush replacement, and stroke
 settings refreshes used by the live brush, quick, color, and floating panel
-callbacks before legacy `Brush` mutation and resource loading continue.
+callbacks. Brush UI execution now dispatches through `BrushUiServices` before
+the legacy `Brush`/panel adapter mutates brush state or loads brush resources.
 `pano_cli plan-canvas-tool` exposes app-core planning for draw/erase/line,
 camera, grid, copy, cut, fill, mask, flood-fill, pick, and touch-lock toolbar
 commands before legacy `Canvas` mode, pen picking, touch-lock, and transform
@@ -1205,7 +1206,9 @@ Results:
   expose live animation-panel planning as JSON automation.
 - `pp_app_core_brush_ui_tests` passed, covering brush color channel validation,
   invalid color rejection, texture-path validation, preset-brush availability,
-  preserve-current-color intent, and stroke-settings refresh intent.
+  preserve-current-color intent, stroke-settings refresh intent, service
+  dispatch ordering, texture/preset execution payloads, and invalid execution
+  payload rejection.
 - `pano_cli_plan_brush_operation_color_smoke`,
   `pano_cli_plan_brush_operation_texture_smoke`,
   `pano_cli_plan_brush_operation_preset_smoke`,