Split Apple platform target and move platform state ownership

docs/modernization/tasks.md

@@ -41,7 +41,8 @@ Completed, blocked, and superseded task history moved to
   `src/node_stroke_preview.cpp`, `src/app.cpp`, `src/app_dialogs.cpp`, and the
   extracted canvas/platform containment files.
 - The platform boundary is not finished:
-  - `pp_platform_api` still compiles Apple implementation files
+  - `pp_platform_api` no longer compiles Apple implementation files, but it
+    still compiles concrete Linux platform sources
   - `platform_apple` no longer reaches `App::I` directly, and Linux FPS title
     reporting now uses an injected callback, but retained Apple bridging and
     broader platform-to-app singleton reach are still open in
@@ -1063,11 +1064,21 @@ layer.
 
 #### ARC-PLT-001 - Split `pp_platform_api` From Concrete Platform Code
 
-Status: Ready
+Status: In Progress
 
 Why now:
 `pp_platform_api` is supposed to be the SDK-free policy and interface layer,
-but it still compiles `src/platform_apple/apple_platform_services.*`.
+and while Apple implementation has now moved out, it still compiles concrete
+Linux platform sources.
+
+Current slice:
+- `pp_platform_api` no longer compiles
+  `src/platform_apple/apple_platform_services.*`.
+- Apple concrete platform code now lives in the new `pp_platform_apple`
+  target, and `panopainter_app` plus `pp_platform_api_tests` now link that
+  concrete target where needed.
+- The dependency direction is cleaner for Apple, but the same split is still
+  incomplete for Linux and the broader concrete platform family.
 
 Write scope:
 - `CMakeLists.txt`
@@ -1128,6 +1139,10 @@ Current slice:
 - retained storage-path state now also lives in
   `src/platform_legacy/legacy_platform_state.*` instead of staying inline in
   `src/platform_legacy/legacy_platform_services.cpp`
+- retained GLFW window hooks/state and retained Apple UI/app handle state now
+  also live in `src/platform_legacy/legacy_platform_state.*`, and
+  `src/platform_legacy/legacy_platform_services.cpp` now consumes those
+  snapshots without direct `App::I` reads in the touched paths
 - retained Apple callback injection and broader `platform_legacy` singleton
   reach are still open
 - The remaining Win32 shell wrappers for close, async lock/swap,
@@ -1160,12 +1175,22 @@ Mini-model packet:
 
 #### ARC-PLT-003 - Remove App-Owned Cross-Platform Handle Storage
 
-Status: Ready
+Status: In Progress
 
 Why now:
 `src/platform_legacy/legacy_platform_services.cpp` and `src/app.h` still keep
 platform-handle state on `App`, which blocks a real `pp_platform_*` shell split.
 
+Current slice:
+- Windows VR session snapshot ownership no longer lives on `App`.
+- `VrSessionSnapshot` now lives behind
+  `src/platform_windows/windows_vr_shell.h` and
+  `read_platform_vr_session_snapshot()` in
+  `src/platform_windows/windows_platform_services.*`, with app-side reads now
+  routed through `App::vr_session_snapshot()`.
+- `App` still owns other platform-facing handles and retained legacy platform
+  state is not fully removed, so this remains a live ownership task.
+
 Write scope:
 - `src/platform_legacy/legacy_platform_services.*`
 - `src/app.h`