Route import and node texture setup through helpers

docs/modernization/roadmap.md

@@ -3021,6 +3021,10 @@ Results:
   stroke composite shader setup helper, while render-task ordering, framebuffer
   copy bounds, sampler/texture binding, and draw execution remain in retained
   canvas-mode code.
+- `Canvas::import_layer` retained object drawing now shares the draw-merge
+  texture shader setup helper for flat and spherical imports, while texture
+  upload, sampler/texture binding, draw callbacks, and object geometry remain in
+  retained Canvas code.
 - `Canvas::thumbnail_generate` checkerboard redraw and final texture blending
   now share the retained draw-merge shader setup helpers, while destination
   copies, sampler/texture binding, readback, and draw execution remain in
@@ -3040,6 +3044,10 @@ Results:
   retained draw-merge texture shader setup helper for `Texture`, `Tex`, and
   `MVP` setup. Texture/sampler binding, atlas setup, blend state, and draw
   execution remain in the node paths.
+- `NodeViewport` preview drawing and `NodePanelGrid` sun-overlay drawing now
+  share the retained draw-merge texture shader setup helper for `Texture`,
+  `Tex`, and `MVP` setup. Texture/sampler binding, viewport/state setup, and
+  draw execution remain in the node paths.
 - `Canvas::stroke_draw_mix` now shares the retained stroke composite shader
   helper for mixer-pass `CompDraw` setup, while preserving its caller-specific
   texture slot uniforms. Mixer framebuffer/scissor state, sampler and texture