Own Web fallback services and trim Win32 session state

docs/modernization/roadmap.md

@@ -70,6 +70,14 @@ What is already real:
 - `pp_app_core`
 
 Latest slice:
+- `src/platform_legacy/legacy_platform_state.*` now exposes an ownable Web
+  platform-services entrypoint plus an explicit binding hook instead of only a
+  retained fallback object.
+- `webgl/src/main.cpp` now owns the Web platform-services implementation and
+  seeds that owned instance into legacy platform state during startup.
+- `src/platform_windows/windows_runtime_shell.*` no longer keeps `HINSTANCE`
+  in the retained main-window session state; the startup/shutdown path now
+  threads the module handle explicitly.
 - `webgl/src/main.cpp` now owns a TU-local legacy `PlatformServices`
   instance and binds that owned service into `App` during `StartApp()`.
 - `android/src/cpp/main.cpp` now owns a function-lifetime legacy

docs/modernization/tasks.md

@@ -78,6 +78,15 @@ Completed, blocked, and superseded task history moved to
   the queue is now ordered by code movement instead.
 
 Current slice:
+- `src/platform_legacy/legacy_platform_state.*` now exposes
+  `create_legacy_web_platform_services()` plus an explicit binding hook for the
+  retained Web service surface.
+- `webgl/src/main.cpp` now owns and binds the Web platform-services
+  implementation explicitly instead of relying only on the retained fallback
+  object in legacy platform state.
+- `src/platform_windows/windows_runtime_shell.*` now threads `HINSTANCE`
+  through the startup/runtime path explicitly instead of keeping it in the
+  retained main-window session state.
 - `webgl/src/main.cpp` now binds an owned legacy `PlatformServices` instance
   instead of reading the process-global fallback directly during `StartApp()`.
 - `android/src/cpp/main.cpp` now binds a function-lifetime owned legacy