Trim recording loop and retain async worker state

docs/modernization/debt.md

@@ -18,6 +18,17 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Reductions
 
+- 2026-06-16: `DEBT-0037` was narrowed again. `App::rec_loop()` in
+  `src/app.cpp` now routes its coherent frame encode/update chunk through a
+  local helper instead of carrying dirty-stroke clearing, equirect PBO
+  creation, the worker-side `yield`, `ImageRef` creation, encode, and frame
+  label refresh inline; retained recording loop control, readback call sites,
+  and MP4 execution remain.
+- 2026-06-16: `DEBT-0003` was narrowed again. The prepared-file worker in
+  `src/app_events.cpp` and the canvas async worker in `src/canvas.cpp` now sit
+  behind named retained local worker-state helpers instead of bare static
+  worker accessors; retained app/canvas singleton reach and broader runtime
+  ownership remain.
 - 2026-06-16: `DEBT-0003` was narrowed again. `src/main.cpp` now keeps Win32
   window handles, GL/task mutex state, stylus timers, splash-dialog state, and
   VR worker state behind one retained local state object instead of separate

docs/modernization/roadmap.md

@@ -133,7 +133,11 @@ Current architecture mismatches that must be treated as real blockers:
   ownership instead of raw global lifetime, and the Windows main-loop/VR
   coordination flags now use `std::atomic` instead of unsynchronized globals,
   while the main Win32 entrypoint now groups window/GL/task/VR state behind a
-  retained local state object instead of separate process-wide globals.
+  retained local state object instead of separate process-wide globals, the
+  prepared-file and canvas async workers now sit behind named retained local
+  worker-state helpers instead of bare static accessors, and `App::rec_loop()`
+  has a smaller local encode/update shell even though the retained recording
+  loop still owns the worker-side readback flow.
 - 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

docs/modernization/tasks.md

@@ -401,9 +401,15 @@ Current slice:
   workers with explicit UI-thread handoff
 - canvas async import/export/save/open and timelapse export now also use owned
   worker queues instead of detached threads
+- `src/app_events.cpp` prepared-file worker ownership and `src/canvas.cpp`
+  async import/export/save/open worker ownership now also sit behind named
+  retained local worker-state helpers instead of bare static worker accessors
 - preview background rendering, recording, and the retained
   `NodePanelGrid::bake_uvs()` worker now also use `std::jthread`, but their
   retained loop/control flow is still open
+- `App::rec_loop()` now routes its frame encode/update chunk through a local
+  helper, and `App::update()` no longer carries the dead update mutex residue,
+  but retained recording loop control and readback ownership are still open
 
 Write scope:
 - `src/canvas.cpp`