Route mask cut composite setup through helper

docs/modernization/debt.md

@@ -18,6 +18,11 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: DEBT-0036 was narrowed again. `CanvasModeMaskCut::apply`
+  retained `CompDraw` shader setup now routes through
+  `legacy_canvas_stroke_composite_services.h`; mask-cut still owns render-task
+  ordering, framebuffer copy bounds, sampler/texture binding, and draw
+  execution.
 - 2026-06-13: DEBT-0036 was narrowed again. Desktop VR retained temporary erase
   and draw shader setup now route through the shared stroke erase/composite
   helpers; VR still owns sampler/texture binding, per-eye/view transforms,

docs/modernization/roadmap.md

@@ -3017,6 +3017,10 @@ Results:
   erase and composite shader setup helpers, while sampler/texture binding,
   per-eye/view transforms, temporary stroke texture selection, and draw
   execution remain in retained VR code.
+- `CanvasModeMaskCut::apply` retained mask-cut compositing now shares the
+  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::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