Centralize canvas blend gate planning

docs/modernization/roadmap.md

@@ -878,6 +878,11 @@ shader-blend gate for layer and primary-brush blend modes while preserving the
 legacy trigger policy; actual canvas stroke execution, dual-brush feedback, and
 pattern feedback are still legacy OpenGL and remain tracked by DEBT-0036 until
 the app calls through renderer services for the whole compositing path.
+`pp_paint_renderer::plan_canvas_blend_gate` now also owns the compatibility
+mapping from persisted layer and brush blend indices to that planner, including
+fallback behavior for unknown nonzero indices. Both `Canvas::draw_merge` and
+`NodeCanvas` panorama rendering consume that shared gate, so the live app no
+longer has duplicate local blend-trigger logic.
 The existing renderer classes are not yet fully
 behind the renderer interfaces.
 
@@ -1602,6 +1607,9 @@ Results:
   `pp_paint_renderer` stroke composite planner for current layer and primary
   brush blend modes, while preserving legacy OpenGL compositing execution under
   DEBT-0036.
+- `NodeCanvas` panorama rendering now consumes the same tested
+  `pp_paint_renderer` canvas blend-gate planner as `Canvas::draw_merge`, so
+  layer and primary-brush blend-trigger compatibility is centralized.
 - Canvas equirectangular import drawing and depth export rendering now route
   depth/blend state and active texture units through the renderer GL backend
   mapping.