Plan document export snapshot routing

docs/modernization/roadmap.md

@@ -729,8 +729,12 @@ pure `pp_paint_renderer` equirectangular PNG generation plus app-core
 collection write/publish execution before retained fallback. Payload-complete
 desktop JPEG equirectangular export now uses the same projection through
 `pp_paint_renderer`, `pp_assets` JPEG encoding, and GPano XMP injection before
-retained fallback. Web handoff, video, and incomplete-readback collection cases
-still delegate to retained `Canvas` writers after readiness reporting.
+retained fallback. `pp_app_core` now owns the document-snapshot export route
+decision used by those live adapters, covering platform support, target support,
+and incomplete renderer-payload fallback; `pano_cli plan-export-snapshot-route`
+exposes the same decision for automation. Web handoff, video, depth writer
+replacement, and incomplete-readback cases still delegate to retained `Canvas`
+writers after route/readiness reporting.
 Depth export now also plans the retained image/depth file targets in
 `pp_app_core` and logs a `pp_paint_renderer` document depth render plan for the
 legacy 1024x1024 perspective render plus per-layer depth pass before falling
@@ -2296,6 +2300,10 @@ Results:
   capture the payload-bearing canvas document snapshot and run the
   renderer-neutral upload report before retained `Canvas` export execution;
   failures are logged and retained export still continues to preserve behavior.
+- `pp_app_core` now owns the document-snapshot export route decision for
+  equirectangular, layer, animation-frame, and cube-face writers, including
+  target/platform support and incomplete renderer-payload fallback reasons.
+  `pano_cli plan-export-snapshot-route` exposes the same policy as JSON.
 - `pp_app_core_document_import_tests` passed, covering wide equirectangular,
   legacy vertical cube strip, regular transform-placement, and invalid-dimension
   import route decisions, equirectangular service dispatch, transform import