Plan app export targets in app core

docs/modernization/build-inventory.md

@@ -397,6 +397,10 @@ Known local toolchain state:
 - `pano_cli plan-document-file` exposes `pp_app_core` document-name
   validation, legacy `.ppi` path construction, and overwrite-prompt decisions
   as JSON and is covered for save-now and existing-target overwrite states.
+- `pano_cli plan-export-target` exposes `pp_app_core` export target planning
+  for image file exports, layer/frame collection directories, picked-directory
+  stems, and MP4 suggested names as JSON and is covered for file, collection,
+  and suggested-name states.
 - `pano_cli simulate-app-session` exposes `pp_app_core` project-open,
   app-close, save, save-as, save-version, and save-before-workflow decisions
   as JSON and is covered for clean, dirty, already-prompting, missing-canvas,
@@ -405,6 +409,9 @@ Known local toolchain state:
   contract for PPI/project files, ABR imports, PPBR imports, inner-dot names,
   and malformed paths before the live `App::open_document` performs UI or
   legacy canvas work.
+- `pp_app_core_document_export_tests` covers export file targets, collection
+  directory/stem targets, picked-directory stems, MP4 suggested names, and
+  invalid export naming inputs.
 - `pp_app_core_document_session_tests` covers clean and dirty app session,
   save-request, save-before-workflow, document file target, and overwrite
   decisions without requiring a window, canvas, or message box.