Bind Win32 app shell and move more legacy platform state

docs/modernization/roadmap.md

@@ -92,6 +92,17 @@ Current hotspot files:
 
 Latest slice:
 
+- The retained Web fallback service object and the Apple storage-path
+  preparation helper now also live in
+  `src/platform_legacy/legacy_platform_state.*` instead of being built inline
+  inside `src/platform_legacy/legacy_platform_services.cpp`, which trims
+  another process-global fallback/service pocket out of the legacy platform
+  shell.
+- The Win32 window procedure, stylus state updates, lifecycle shutdown path,
+  and VR shell callback wiring no longer reach `App::I` directly; the live
+  Windows shell now binds the active `App*` explicitly through
+  `src/platform_windows/windows_runtime_shell.*`, leaving `App::I` only at
+  the entry/shutdown composition edge in the touched Win32 path.
 - The full retained Apple document bridge construction no longer lives inline
   in `src/platform_legacy/legacy_platform_services.cpp`; it now lives behind
   `active_legacy_apple_document_platform_services()` in

docs/modernization/tasks.md

@@ -1202,6 +1202,15 @@ Why now:
 platform-handle state on `App`, which blocks a real `pp_platform_*` shell split.
 
 Current slice:
+- The retained Web fallback service object and the Apple storage-path
+  preparation helper now also live in
+  `src/platform_legacy/legacy_platform_state.*` instead of being built inline
+  in `src/platform_legacy/legacy_platform_services.cpp`, which trims another
+  retained fallback/state pocket out of the legacy platform shell.
+- The touched Win32 shell path no longer reaches `App::I` directly for
+  window-procedure dispatch, stylus state updates, lifecycle shutdown, or VR
+  callback/thread setup; `src/platform_windows/windows_runtime_shell.*` now
+  binds the active `App*` explicitly and clears that binding on shutdown.
 - Windows VR session snapshot ownership no longer lives on `App`.
 - `VrSessionSnapshot` now lives behind
   `src/platform_windows/windows_vr_shell.h` and