Extract PPBR package path validation

docs/modernization/roadmap.md

@@ -788,6 +788,13 @@ through the app-core brush package export executor and
 collection, legacy `Image` header ownership, desktop worker-thread export,
 mobile/Web save completion, `NodePanelBrushPreset::export_ppbr`, and existing
 success messages while retained execution remains tracked under `DEBT-0047`.
+PPBR package header validation and export target/data-directory planning now
+live in `pp_assets::brush_package` and are exercised by
+`pp_assets_brush_package_tests` plus `pano_cli plan-brush-package-export`.
+The live PPBR import/export path consumes those helpers, while legacy
+Serializer/Image payload reading, stroke preview generation, preset storage,
+and the historical permissive version check remain tracked under `DEBT-0047`
+and `DEBT-0049`.
 
 Implementation tasks:
 
@@ -1396,6 +1403,13 @@ Results:
   `pano_cli_plan_brush_package_import_abr_smoke`,
   `pano_cli_plan_brush_package_import_rejects_empty_path`, and
   `pano_cli_plan_brush_package_import_rejects_unknown_kind`.
+- `PanoPainter`, `pp_assets_brush_package_tests`,
+  `pp_app_core_brush_package_export_tests`, and `pano_cli` built after PPBR
+  header validation and export path/data-directory planning moved into
+  `pp_assets`.
+- Focused PPBR asset CTest coverage passed for `pp_assets_brush_package_tests`
+  and the brush package export CLI tests, including path-without-directory
+  rejection and legacy no-export-data data-directory planning.
 - `pp_app_core_document_recording_tests` passed, covering recording start/stop,
   clear, platform recorded-file cleanup, frame-count reset, export progress
   totals, and oversized progress-total clamping.