Drain deferred FX parks before the view model is serialized; re-validate track handles per intent; pin the restore-plan round trip

src/shell/actions/design_view_actions.cpp

@@ -26,6 +26,7 @@
 #include "shell/capture/track_guid.h"    // shared MediaTrack* -> canonical GUID key
 #include "shell/panel/panel_window.h"    // bankPanelInvalidate — footer toggle repaint
 #include "shell/view/view.h"             // applyMode + mintManagedLanes (D2 shell)
+#include "shell/view/view_fx_park.h"     // drainDeferredFxParks — see persistViewState
 
 #define REAPERAPI_MINIMAL
 #define REAPERAPI_WANT_CountSelectedTracks
@@ -138,6 +139,12 @@ std::vector<RetagItem> selectedRetagItems() {
 // the project is unsaved, prompts Save-As first (mirrors the flow capture uses) —
 // DAW-ONLY: Main_SaveProject(proj, true) blocks until the dialog is dismissed.
 void persistViewState() {
+    // BEFORE the model is serialized, and before the Save-As below can write a
+    // .rpp: a deferred FX restore leaves the chain offline while the model has
+    // already dropped the snapshot that would replan it. Why that combination is
+    // unrecoverable on reopen is at drainDeferredFxParks.
+    drainDeferredFxParks();
+
     if (!g_session->view().membership().empty()) {
         ReaProject* proj = EnumProjects(-1, nullptr, 0);
         if (proj) {