Move early canvas GL mappings to renderer gl

docs/modernization/roadmap.md

@@ -758,6 +758,10 @@ Results:
   filters and wraps, and cube-strip import channel formats through the renderer
   GL backend mapping. The clamp-to-border sampler wrap is now cataloged and
   tested in `pp_renderer_gl`.
+- Early canvas draw helpers now route pick readbacks, stroke mixer depth/scissor
+  and blend state, saved viewport/clear-state queries, active texture units,
+  fallback 2D texture unbinds, and stroke background copy targets 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.