Remove legacy platform shim from root app graph

cmake/PanoPainterSources.cmake

@@ -180,8 +180,6 @@ set(PP_PANOPAINTER_APP_SOURCES
     src/legacy_document_open_services.h
     src/legacy_document_session_services.cpp
     src/legacy_document_session_services.h
-    src/platform_legacy/legacy_platform_services.cpp
-    src/platform_legacy/legacy_platform_services.h
     ${PP_PLATFORM_WEB_SOURCES}
     src/version.cpp
 )

docs/modernization/debt.md

@@ -18,6 +18,11 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Reductions
 
+- 2026-06-17: `DEBT-0017`/`DEBT-0055` were narrowed again.
+  `src/platform_legacy/legacy_platform_services.*` is no longer compiled into
+  the root `panopainter_app` source graph. The retained shim still exists on
+  disk for non-root compatibility consumers, but the root Windows/Android/Apple
+  modernization matrix no longer links it into the live app target.
 - 2026-06-17: `DEBT-0017`/`DEBT-0050`/`DEBT-0053`/`DEBT-0057` were narrowed
   again. `webgl/src/main.cpp` now binds a concrete
   `src/platform_web/web_platform_services.*` `PlatformServices` instance

docs/modernization/roadmap.md

@@ -70,6 +70,13 @@ What is already real:
 - `pp_app_core`
 
 Latest slice:
+- `cmake/PanoPainterSources.cmake` no longer adds
+  `src/platform_legacy/legacy_platform_services.*` to
+  `PP_PANOPAINTER_APP_SOURCES`, so the root `panopainter_app` target graph
+  stops compiling and linking that retained fallback shim.
+- The retained `platform_legacy` adapter still exists on disk for non-root
+  compatibility paths, but it is no longer part of the root modernization app
+  graph validated by the quiet Windows/Android/Apple matrix.
 - `src/platform_web/web_platform_services.*` now owns the concrete WebGL
   `PlatformServices` implementation as well as the narrower
   `WebPlatformServices` helper surface.

docs/modernization/tasks.md

@@ -84,6 +84,13 @@ Completed, blocked, and superseded task history moved to
   the queue is now ordered by code movement instead.
 
 Current slice:
+- `cmake/PanoPainterSources.cmake` no longer adds
+  `src/platform_legacy/legacy_platform_services.*` to
+  `PP_PANOPAINTER_APP_SOURCES`.
+- The root `panopainter_app` modernization graph no longer compiles or links
+  the retained `platform_legacy` fallback shim.
+- The retained file still exists on disk for non-root compatibility consumers,
+  but it is now outside the validated root app target graph.
 - `src/platform_web/web_platform_services.*` now owns the concrete Web
   `PlatformServices` implementation and `webgl/src/main.cpp` now binds that
   owned service directly at the WebGL entrypoint.