Promote RND-005 preview gpu task

docs/modernization/tasks.md

@@ -355,6 +355,34 @@ ctest --preset desktop-gpu --build-config Debug --output-on-failure
 ctest --preset desktop-fast --build-config Debug -R "pp_renderer_gl|pp_paint_renderer" --output-on-failure
 ```
 
+### RND-005 - Add Desktop GPU Preview Golden Gate
+
+Status: Ready
+Score: +2 hardening and future backend readiness
+Debt: `DEBT-0036`
+Scope: `tests/`, `CMakeLists.txt`, renderer test helpers only
+
+Goal:
+
+Create the next non-default `desktop-gpu` golden/readback test for the preview
+composite path so the renderer parity lane covers live stroke preview output,
+not just the broader renderer backend helpers.
+
+Done Checks:
+
+- `ctest --preset desktop-gpu --build-config Debug` has a real preview/compositor
+  golden gate.
+- The test is skipped with a clear message when no GPU/context is available.
+- The roadmap and debt log describe the preview output the golden covers and
+  what remains.
+
+Validation:
+
+```powershell
+ctest --preset desktop-gpu --build-config Debug --output-on-failure
+ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_compositor|pp_paint_renderer_stroke_execution" --output-on-failure
+```
+
 ### PLT-001 - Split Apple Picker/Browse Service From Legacy Platform Adapter
 
 Status: Done