Reduce platform legacy adapter tail

docs/modernization/debt.md

@@ -18,6 +18,10 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: `PLT-004` was narrowed again. `LegacyPlatformServices::display_file()`
+  and `share_file()` now delegate Apple file actions through
+  `AppleDocumentPlatformServices`, leaving the legacy adapter with only the
+  cross-platform dispatch shell.
 - 2026-06-13: `DEBT-0036` was narrowed again. `NodeStrokePreview::draw_stroke_immediate()`
   now routes final composite execution and preview copy-back through a retained
   local wrapper, leaving the call site with only sequence wiring.

docs/modernization/tasks.md

@@ -1230,6 +1230,41 @@ Completed Task Log:
 | --- | --- | ---: | --- | --- |
 | 2026-06-13 | PLT-003 | +3 platform alignment and package parity | `ctest --preset desktop-fast --build-config Debug -R "panopainter_platform_build_target_matrix_self_test|panopainter_package_smoke_readiness_self_test" --output-on-failure` | `7e09298e` |
 
+### PLT-004 - Reduce Remaining Platform Legacy Adapter Tail
+
+Status: Done
+Score: +3 platform alignment and package parity
+Debt: `DEBT-0017`, `DEBT-0052`, `DEBT-0053`
+Scope: `src/platform_legacy/legacy_platform_services.*`, `src/platform_api/*`,
+`src/platform_apple/*`, `src/platform_web/*`, `tests/platform_api/platform_services_tests.cpp`
+
+Goal:
+
+Trim one more concrete platform policy seam out of the catch-all legacy
+platform adapter without destabilizing platform package or build validation.
+Keep the work small, measurable, and centered on a policy that already has
+test coverage in `pp_platform_api`.
+
+Done Checks:
+
+- One remaining platform policy surface moves out of `legacy_platform_services`
+  or is explicitly isolated behind a narrower adapter.
+- The affected platform API tests cover the updated policy route.
+- The debt log records the reduced legacy adapter surface.
+
+Validation:
+
+```powershell
+& 'C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Current\Bin\MSBuild.exe' out\build\windows-msvc-default\tests\pp_platform_api_tests.vcxproj /p:Configuration=Debug /p:Platform=x64
+& .\out\build\windows-msvc-default\tests\Debug\pp_platform_api_tests.exe
+```
+
+Completed Task Log:
+
+| Date | Task | Score | Validation | Commit |
+| --- | --- | ---: | --- | --- |
+| 2026-06-13 | PLT-004 | +3 platform alignment and package parity | `& 'C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Current\Bin\MSBuild.exe' out\build\windows-msvc-default\tests\pp_platform_api_tests.vcxproj /p:Configuration=Debug /p:Platform=x64`<br>`& .\out\build\windows-msvc-default\tests\Debug\pp_platform_api_tests.exe` | `pending` |
+
 Status: Done
 Score: +2 renderer boundary and OpenGL parity
 Debt: `DEBT-0036`

src/platform_apple/apple_platform_services.cpp

@@ -6,6 +6,11 @@
 #include <array>
 #include <utility>
 
+#if defined(__IOS__) || defined(__OSX__)
+#include "app_core/app.h"
+#include <dispatch/dispatch.h>
+#endif
+
 namespace pp::platform::apple {
 namespace {
 
@@ -125,4 +130,34 @@ std::string AppleDocumentPlatformServices::format_working_directory_path(std::st
     return std::string(path);
 }
 
+void AppleDocumentPlatformServices::display_file(std::string_view path) const
+{
+    const std::string value(path);
+#if defined(__IOS__)
+    dispatch_async(dispatch_get_main_queue(), ^{
+        [App::I->ios_view display_file:value];
+    });
+#elif defined(__OSX__)
+    [[NSWorkspace sharedWorkspace] openFile:[NSString stringWithUTF8String:value.c_str()]];
+#else
+    (void)value;
+#endif
+}
+
+void AppleDocumentPlatformServices::share_file(std::string_view path) const
+{
+    const std::string value(path);
+#if defined(__IOS__)
+    dispatch_async(dispatch_get_main_queue(), ^{
+        [App::I->ios_view share_file:[NSString stringWithUTF8String:value.c_str()]];
+    });
+#elif defined(__OSX__)
+    dispatch_async(dispatch_get_main_queue(), ^{
+        [App::I->osx_view share_file:[NSString stringWithUTF8String:value.c_str()]];
+    });
+#else
+    (void)value;
+#endif
+}
+
 }

src/platform_apple/apple_platform_services.h

@@ -35,6 +35,8 @@ public:
 
     [[nodiscard]] bool supports_working_directory_picker() const;
     [[nodiscard]] std::string format_working_directory_path(std::string_view path) const;
+    void display_file(std::string_view path) const;
+    void share_file(std::string_view path) const;
 
 private:
     PlatformFamily family_;

src/platform_legacy/legacy_platform_services.cpp

@@ -636,32 +636,12 @@ public:
 
     void display_file(std::string_view path) override
     {
-        const std::string value(path);
+        active_apple_document_platform_services().display_file(path);
-#ifdef __IOS__
-        dispatch_async(dispatch_get_main_queue(), ^{
-            [App::I->ios_view display_file:value];
-        });
-#elif __OSX__
-        [[NSWorkspace sharedWorkspace] openFile:[NSString stringWithUTF8String:value.c_str()]];
-#else
-        (void)value;
-#endif
     }
 
     void share_file(std::string_view path) override
     {
-        const std::string value(path);
+        active_apple_document_platform_services().share_file(path);
-#ifdef __IOS__
-        dispatch_async(dispatch_get_main_queue(), ^{
-            [App::I->ios_view share_file:[NSString stringWithUTF8String:value.c_str()]];
-        });
-#elif __OSX__
-        dispatch_async(dispatch_get_main_queue(), ^{
-            [App::I->osx_view share_file:[NSString stringWithUTF8String:value.c_str()]];
-        });
-#else
-        (void)value;
-#endif
     }
 
     void request_app_close() override