Own brush workers and thin preview/platform seams

docs/modernization/tasks.md

@@ -42,12 +42,13 @@ Completed, blocked, and superseded task history moved to
   `src/node_canvas.cpp`, `src/app.cpp`, and `src/app_dialogs.cpp`.
 - The platform boundary is not finished:
   - `pp_platform_api` still compiles Apple implementation files
-  - Apple and Linux platform services still reach `App::I`
+  - Apple platform services still reach `App::I`
+  - Linux FPS title reporting now uses an injected callback, but broader
+    platform-to-app singleton reach is still open
   - `platform_legacy` is still part of the live app shell
 - The app runtime boundary is not finished:
   - render/UI queues are static `App` state
-  - detached workers still launch from canvas, cloud, brush, grid, preview, and
-    event code
+  - detached workers still launch from canvas, grid, preview, and event code
   - thread-affinity rules are enforced by convention and asserts instead of
     explicit runtime contracts
 - The UI ownership boundary is not finished:
@@ -114,12 +115,17 @@ Mini-model packet:
 
 #### ARC-RND-002 - Isolate Preview And Canvas View Render Execution
 
-Status: Ready
+Status: In Progress
 
 Why now:
 `src/node_stroke_preview.cpp` and `src/node_canvas.cpp` still own a large amount
 of live preview/canvas render sequencing around the renderer boundary.
 
+Current slice:
+- `NodeStrokePreview` final composite plus preview-texture copy now route
+  through `legacy_node_stroke_preview_execution_services.h`, but the preview
+  node still owns most live-pass and retained GL resource execution.
+
 Write scope:
 - `src/node_stroke_preview.cpp`
 - `src/node_canvas.cpp`
@@ -330,13 +336,20 @@ Mini-model packet:
 
 #### ARC-APP-005 - Replace Detached App Workers With Joinable Or Service-Owned Work
 
-Status: Ready
+Status: In Progress
 
 Why now:
 Canvas imports/exports/saves, cloud transfer, brush import/export, grid
 lightmap work, stroke preview, and event persistence still launch detached
 threads. That is not a safe modernization foundation.
 
+Current slice:
+- app-owned render/UI runtime queues and cloud worker ownership are already
+  moving behind owned runtime/service objects
+- brush package import/export now use service-owned `std::jthread` workers and
+  UI-thread completion handoff
+- canvas, grid, preview, and event-side detached work is still open
+
 Write scope:
 - `src/canvas.cpp`
 - `src/app_cloud.cpp`
@@ -525,12 +538,18 @@ Mini-model packet:
 
 #### ARC-PLT-002 - Remove `App::I` Reach From Apple And Linux Services
 
-Status: Ready
+Status: In Progress
 
 Why now:
 The current Apple and Linux service files still call into the app singleton,
 which means the platform layer is not a platform layer yet.
 
+Current slice:
+- Linux FPS title updates now route through an injected callback installed from
+  `App::set_platform_services()`
+- Apple singleton reach and the remaining platform callback surface are still
+  open
+
 Write scope:
 - `src/platform_apple/*`
 - `src/platform_linux/*`