Use shared parallel loop for grid lightmap bake

docs/modernization/build-inventory.md

@@ -230,8 +230,9 @@ Known local toolchain state:
 - `src/legacy_grid_ui_services.*` is the current UI-shell bridge for grid
   heightmap picker/load/reload/clear, lightmap render, and heightmap commit
   execution. It keeps those live paths on the `pp_app_core` contracts while
-  legacy image loading, OpenGL texture updates, nanort baking/progress, and
-  `Canvas::draw_objects` execution remain tracked by `DEBT-0024`.
+  legacy image loading, OpenGL texture updates, shared `parallel_for` CPU
+  lightmap baking/progress, and `Canvas::draw_objects` execution remain tracked
+  by `DEBT-0024`.
 - `src/legacy_quick_ui_services.*` is the current UI-shell bridge for quick
   brush/color slot selection, popup routing, mini-state restore, and mini-state
   reset execution. It keeps those live paths on the `pp_app_core` contracts
@@ -351,7 +352,8 @@ Known local toolchain state:
   `NodePanelGrid` heightmap preview and lightmap baking also consume
   backend-owned texture readback formats, sampler filters, depth/blend state,
   depth clears, viewport queries, color-mask booleans, active texture units,
-  and float render-target formats.
+  and float render-target formats; CPU lightmap row dispatch now uses shared
+  `parallel_for` instead of platform-specific worker APIs.
   Legacy `util.cpp` OpenGL error naming and `gl_state` save/restore also
   consume backend-owned error codes, state queries, framebuffer targets,
   texture binding targets, and active texture units.