Own grid workers and thin Apple platform bridge

docs/modernization/roadmap.md

@@ -94,10 +94,10 @@ Current architecture mismatches that must be treated as real blockers:
 
 - `pp_platform_api` still compiles Apple implementation files instead of only
   platform-neutral policy and interface code.
-- `src/platform_apple/apple_platform_services.cpp` and
-  parts of the concrete platform layer still reach `App::I`; Linux FPS title
-  reporting now uses an injected callback, but Apple singleton reach and other
-  platform/app coupling remain.
+- `src/platform_apple/apple_platform_services.cpp` no longer reaches `App::I`
+  directly, and Linux FPS title reporting now uses an injected callback, but
+  retained Apple bridging in `platform_legacy` and other platform/app coupling
+  remain.
 - `src/platform_legacy/legacy_platform_services.*` is still part of the live
   app shell.
 - `pp_panopainter_ui` still depends on `pp_legacy_app`.
@@ -107,7 +107,8 @@ Current architecture mismatches that must be treated as real blockers:
   rather than thin composition/binding surfaces.
 - `App`, `Canvas`, `Node`, retained workers, and platform entrypoints still use
   global singleton reach, raw observer pointers, detached `std::thread`
-  launches, and ad hoc mutex/condition-variable ownership.
+  launches in several canvas/export/preview paths, and ad hoc
+  mutex/condition-variable ownership.
 - Modern C++23 usage exists in extracted components, especially `std::span`,
   explicit result/status objects, and a few concepts, but the live app still
   does not consistently express ownership, thread affinity, or renderer