Split Linux FPS title reporting

docs/modernization/debt.md

@@ -52,6 +52,9 @@ agent or engineer to remove them without reconstructing context from chat.
   and `share_file()` now delegate Apple file actions through
   `AppleDocumentPlatformServices`, leaving the legacy adapter with only the
   cross-platform dispatch shell.
+- 2026-06-13: `PLT-005` was narrowed again. Linux rendered-frame title updates
+  now route through `src/platform_linux/linux_platform_services.*`; the legacy
+  platform adapter still owns the surrounding 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

@@ -1294,6 +1294,42 @@ Completed Task Log:
 | --- | --- | ---: | --- | --- |
 | 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` | `6ba98ee` |
 
+### PLT-005 - Split Linux FPS Title Reporting From Legacy Platform Adapter
+
+Status: Done
+Score: +1 platform alignment and package parity
+Debt: `DEBT-0017`, `DEBT-0052`
+Scope: `src/platform_legacy/legacy_platform_services.cpp`,
+`src/platform_linux/*`, `tests/platform_api_tests.cpp` if coverage is needed
+
+Goal:
+
+Move Linux rendered-frame FPS title updates out of the catch-all legacy
+platform adapter into a named Linux platform service boundary. Preserve the
+current Linux title update behavior and keep non-Linux behavior unchanged.
+
+Done Checks:
+
+- `src/platform_legacy/legacy_platform_services.cpp` no longer owns the Linux
+  FPS-title update branch.
+- Linux rendered-frame reporting still updates the title as before.
+- The debt log records the reduced Linux platform tail.
+
+Validation:
+
+```powershell
+ctest --preset desktop-fast --build-config Debug -R pp_platform_api_tests --output-on-failure
+cmake --build --preset windows-msvc-default --config Debug --target pp_platform_api_tests
+```
+
+Completed Task Log:
+
+| Date | Task | Score | Validation | Commit |
+| --- | --- | ---: | --- | --- |
+| 2026-06-13 | PLT-005 | +1 platform alignment and package parity | `ctest --preset desktop-fast --build-config Debug -R pp_platform_api_tests --output-on-failure`; `cmake --build --preset windows-msvc-default --config Debug --target pp_platform_api_tests` | `pending` |
+
+### STR-010 - Extract Remaining Draw Merge Composite Orchestration
+
 Status: Done
 Score: +2 renderer boundary and OpenGL parity
 Debt: `DEBT-0036`