Route canvas layer GL state through backend

docs/modernization/roadmap.md

@@ -1095,7 +1095,8 @@ Simple UI text, text-input, border, scroll, and animation timeline draw paths
 now also delegate blend-state tokens to `pp_renderer_gl`.
 Canvas layer cube/equirect generation, clear, restore, and snapshot paths now
 also delegate cube/2D texture targets, active texture units, blend/clear state,
-and RGBA8 read/write pixel mapping to `pp_renderer_gl`.
+viewport execution, target-aware framebuffer-to-texture copies, and RGBA8
+read/write pixel mapping to `pp_renderer_gl`.
 `NodePanelGrid` heightmap preview and lightmap baking now delegate texture
 readback formats, sampler filters, depth/blend state, depth clears, viewport
 queries, color-mask booleans, active texture units, and float render-target
@@ -2045,6 +2046,10 @@ Results:
 - Canvas layer merge rendering and explicit layer-merge compositing now route
   depth/blend state, active texture units, fallback 2D texture unbinds, and
   merge framebuffer copy targets through the renderer GL backend mapping.
+- Canvas layer cube/equirect generation and frame clears now route blend state,
+  active texture units, viewport execution, color clears, and cube-face
+  framebuffer-to-texture copies through tested renderer GL backend dispatch
+  contracts.
 - Canvas draw-merge shader-blend selection now consumes the extracted
   `pp_paint_renderer` stroke composite planner for current layer and primary
   brush blend modes, while preserving legacy OpenGL compositing execution under