Remove dead legacy storage fallback and hide GLFW state

docs/modernization/roadmap.md

@@ -70,6 +70,13 @@ What is already real:
 - `pp_app_core`
 
 Latest slice:
+- `src/platform_legacy/legacy_platform_state.*` no longer carries the dead
+  generic storage-path singleton for the current runtime matrix.
+- `src/platform_legacy/legacy_platform_services.cpp` now drops the dead generic
+  storage-path fallback read; only the platform-specific storage-path branches
+  remain live.
+- `src/legacy_app_startup_services.cpp` no longer seeds the dead generic
+  storage-path fallback state on non-Android startup.
 - `src/platform_legacy/legacy_platform_services.cpp` now reads Android storage
   paths from Android-owned retained state instead of the shared legacy
   storage-path singleton.
@@ -80,6 +87,9 @@ Latest slice:
   `src/platform_legacy/legacy_platform_state.*` now route the Linux FPS-title
   callback through a narrow legacy GLFW title helper instead of reaching into
   retained GLFW window state from `App::set_platform_services(...)`.
+- `src/platform_legacy/legacy_platform_state.h` no longer exports the raw
+  retained GLFW window-state accessor; callers now go through narrow GLFW
+  helpers only.
 - `src/platform_apple/apple_platform_state.cpp` no longer reads Apple storage
   paths from `pp::platform::legacy::active_legacy_storage_paths()`;
   Apple-owned retained state now carries that path bundle.

docs/modernization/tasks.md

@@ -78,6 +78,13 @@ Completed, blocked, and superseded task history moved to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.*` no longer keeps the dead
+  generic storage-path singleton for the current platform matrix.
+- `src/platform_legacy/legacy_platform_services.cpp` now returns only
+  platform-specific storage-path branches; the dead generic fallback read is
+  gone.
+- `src/legacy_app_startup_services.cpp` no longer writes the dead generic
+  storage-path fallback state on non-Android startup.
 - `src/platform_legacy/legacy_platform_services.cpp` plus
   `src/platform_legacy/legacy_platform_state.*` now give Android its own
   retained storage-path surface instead of reading the shared legacy singleton.
@@ -87,6 +94,8 @@ Current slice:
   `src/platform_legacy/legacy_platform_state.*` now use a narrow GLFW title
   helper for Linux FPS-title updates instead of direct retained-window access
   in the app event layer.
+- `src/platform_legacy/legacy_platform_state.h` no longer exports the raw
+  retained GLFW window accessor.
 - `src/platform_apple/apple_platform_state.cpp` now reads Apple storage paths
   from Apple-owned retained state rather than the shared legacy storage-path
   singleton.