Extend app input planning to UI state

docs/modernization/debt.md

@@ -100,11 +100,14 @@ agent or engineer to remove them without reconstructing context from chat.
   render-target recreation, and OpenGL/UI drawing remain in the legacy app.
 - 2026-06-05: DEBT-0003 was narrowed. Pointer coordinate normalization,
   mouse designer-first routing, gesture midpoint/delta math, touch/key
-  main-layout routing, and VR spacebar camera-sync intent are now tested
-  `pp_app_core` input plans consumed by `App::mouse_*`, `App::gesture_*`,
-  `App::touch_tap`, `App::key_*`, and `pano_cli plan-app-input`; retained
-  `MouseEvent`/`GestureEvent`/`TouchEvent`/`KeyEvent` construction and legacy
-  `Node` event dispatch remain in the app shell.
+  main-layout routing, VR spacebar camera-sync intent, UI visibility toggling,
+  and stylus touch-lock attachment are now tested `pp_app_core` input plans
+  consumed by `App::mouse_*`, `App::gesture_*`, `App::touch_tap`,
+  `App::key_*`, `App::toggle_ui`, `App::set_stylus`, and
+  `pano_cli plan-app-input`; retained
+  `MouseEvent`/`GestureEvent`/`TouchEvent`/`KeyEvent` construction,
+  UI child-node mutation, and legacy `Node` event dispatch remain in the app
+  shell.
 - 2026-06-05: DEBT-0003 was narrowed again. Shutdown cleanup staging for
   UI-state save, stroke-preview renderer shutdown, recording stop,
   texture/shader invalidation, layout unload, UI render-target and face-plane