Move canvas mode GL mappings to renderer gl

docs/modernization/build-inventory.md

@@ -202,6 +202,9 @@ Known local toolchain state:
   Desktop VR drawing also consumes backend-owned scissor/depth/blend state,
   depth clear masks, active texture units, and fallback 2D texture unbind
   targets while retaining the existing VR SDK/platform bridge shape.
+  Canvas mode overlay, mask, and transform paths also consume backend-owned
+  blend/depth state, active texture units, 2D texture copy targets, and RGBA8
+  readback format tokens.
 - `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.

docs/modernization/roadmap.md

@@ -746,6 +746,9 @@ Results:
   depth clears, active texture units, and fallback 2D texture unbinds through
   the renderer GL backend mapping; platform VR SDK bridges remain isolated for
   later platform-shell extraction.
+- Canvas mode overlay, mask, and transform paths now route generic OpenGL
+  blend/depth state, active texture units, 2D copy targets, and RGBA8
+  readback formats through the renderer GL backend mapping.
 - Known remaining warnings: legacy project/vendor diagnostics, Visual Studio
   vcpkg-manifest warning, `LNK4099` missing libyuv PDBs, and `LNK4098` runtime
   library conflict from retained vendor binaries.