Route app shutdown staging through app core

docs/modernization/build-inventory.md

@@ -246,6 +246,11 @@ Known local toolchain state:
   `App::draw`, and `pano_cli plan-app-frame`; retained layout traversal,
   toolbar widget writes, canvas stroke drawing, VR UI render-target drawing,
   main target binding, and OpenGL/UI drawing remain in the legacy app.
+- `src/app_core/app_shutdown.h` owns the current shutdown cleanup staging
+  consumed by `App::terminate` and `pano_cli plan-app-shutdown`; retained
+  UI-state save, recording stop, resource invalidation, layout unload,
+  render-target/mesh destruction, and panel-node release remain in the legacy
+  app.
 - `src/legacy_app_preference_services.*` is the current app-shell bridge for
   options-menu preference execution. It keeps UI scale, viewport scale, RTL,
   VR mode, VR-controller, auto-timelapse, and canvas cursor-mode callbacks on
@@ -832,6 +837,10 @@ Known local toolchain state:
 - `pp_app_core_app_frame_tests` covers the legacy initial surface default,
   idle/redraw/animation update gating, canvas-stroke draw eligibility, VR UI
   visibility, main UI suppression in VR-only mode, and redraw reset planning.
+- `pp_app_core_app_shutdown_tests` covers legacy shutdown cleanup staging for
+  UI-state save, stroke-preview renderer shutdown, recording stop,
+  texture/shader invalidation, layout unload, render-target/mesh destruction,
+  panel-node release, and quick-mode cleanup.
 - `pp_platform_api_tests` covers service dispatch for clipboard read/write,
   empty clipboard writes, cursor visibility, virtual-keyboard visibility,
   external file display, file sharing, VR lifecycle, layout/asset file load

docs/modernization/debt.md

@@ -20,7 +20,7 @@ agent or engineer to remove them without reconstructing context from chat.
 
 - 2026-06-04: DEBT-0009 was narrowed. `platform-build.ps1` and
   `platform-build.sh` now include the current headless component/test matrix,
-  including brush-package coverage and the app-core startup/frame/file/document/
+  including brush-package coverage and the app-core startup/frame/shutdown/file/document/
   brush/canvas/history/grid/toolbar/tools/about/preferences/status automation
   tests, and `panopainter_platform_build_target_matrix_self_test` now verifies
   the wrapper defaults against the current CMake test executables. On
@@ -97,6 +97,13 @@ agent or engineer to remove them without reconstructing context from chat.
   consumed by `App::create`, `App::update`, `App::draw`, and
   `pano_cli plan-app-frame`; retained layout traversal, toolbar widget writes,
   and OpenGL/UI drawing remain in the legacy app.
+- 2026-06-05: DEBT-0003 was narrowed again. Shutdown cleanup staging for
+  UI-state save, stroke-preview renderer shutdown, recording stop,
+  texture/shader invalidation, layout unload, UI render-target and face-plane
+  destruction, panel-node release, and quick-mode cleanup now goes through
+  tested `pp_app_core` plans consumed by `App::terminate` and
+  `pano_cli plan-app-shutdown`; retained cleanup execution remains in the
+  legacy app.
 - 2026-06-04: DEBT-0036 was narrowed again. Canvas stroke commit,
   thumbnail, and object-draw history paths now query saved blend state through
   tested `pp_renderer_gl` capability-state dispatch; CanvasLayer equirect

docs/modernization/roadmap.md

@@ -203,6 +203,11 @@ gating, canvas-stroke drawing, VR UI drawing, main UI drawing, and redraw reset
 now live in `pp_app_core`; `App::create`, `App::update`, `App::draw`, and
 `pano_cli plan-app-frame` consume those plans while retained layout traversal
 and OpenGL/UI drawing stay in the legacy app.
+Shutdown lifecycle staging for UI-state save, stroke-preview renderer shutdown,
+recording stop, texture/shader invalidation, layout unload, render-target
+destruction, panel-node release, and quick-mode cleanup now lives in
+`pp_app_core`; `App::terminate` and `pano_cli plan-app-shutdown` consume that
+plan while retained cleanup execution stays in the legacy app.
 `panopainter_app` is now a real static target that owns app orchestration
 sources, app version metadata, and version-header generation.
 `pp_panopainter_ui` now owns app-specific modal, dialog, panel, canvas,
@@ -1291,7 +1296,7 @@ standard x64/arm64, Android Quest arm64, Android Focus/Wave arm64,
 Emscripten/WebGL, macOS, iOS device, and iOS simulator. `platform-build`
 automation now builds the current headless component matrix, including
 `pp_platform_api`, `pp_app_core`, platform API tests, brush-package tests, and
-the current app-core startup/frame/file/document/brush/canvas/history/grid/toolbar/
+the current app-core startup/frame/shutdown/file/document/brush/canvas/history/grid/toolbar/
 tools/about/preferences/status automation tests. The PowerShell wrapper also
 normalizes comma-separated `-Presets` and `-Targets` values for reliable
 machine-driven partial matrix checks. `panopainter_platform_build_target_matrix_self_test`
@@ -1653,6 +1658,11 @@ Results:
 - Focused frame CTest coverage passed for `pp_app_core_app_frame_tests`,
   `pano_cli_plan_app_frame_vr_smoke`, and
   `pano_cli_plan_app_frame_idle_missing_canvas_smoke`.
+- `PanoPainter`, `pp_app_core_app_shutdown_tests`, and `pano_cli` built after
+  shutdown cleanup staging moved into `pp_app_core`.
+- Focused shutdown CTest coverage passed for `pp_app_core_app_shutdown_tests`,
+  `pano_cli_plan_app_shutdown_smoke`, and
+  `pano_cli_plan_app_shutdown_rejects_unknown_option`.
 - `PanoPainter`, `pp_app_core_brush_package_export_tests`, and `pano_cli` built
   after PPBR brush package export request validation and dispatch moved behind
   app-core brush package services.