Move grid panel render mapping to renderer gl

docs/modernization/build-inventory.md

@@ -182,6 +182,10 @@ Known local toolchain state:
   Canvas layer cube/equirect generation, clear, restore, and snapshot paths
   also consume backend-owned cube/2D texture targets, active texture units,
   blend/clear state, and RGBA8 read/write pixel mapping.
+  `NodePanelGrid` heightmap preview and lightmap baking also consume
+  backend-owned texture readback formats, sampler filters, depth/blend state,
+  depth clears, viewport queries, color-mask booleans, active texture units,
+  and float render-target formats.
 - `windows-msvc-vcpkg-headless` validates manifest install/configure/build/test
   for the current headless component matrix; see DEBT-0007 for remaining app
   and platform triplet migration.