Split FX out of the park plan: flag-only plans, derived online-first FX work list, two-half record release, applied-state fingerprint

src/shell/view/view_fx_park.cpp

@@ -203,15 +203,17 @@ TrackApplyResult restoreTrack(ViewModeModel& model, const std::string& guid, Med
     for (const FxOfflineWrite& w : res.writes)
         if (setOfflineIfChanged(tr, w.fxIndex, w.offline)) out.fxMoved = out.wrote = true;
     out.drops = res.drops;
+    // The chain is back online HERE, which is the only thing that spends the FX half.
+    model.releaseSnapshotFx(guid);
 
     if (applyFlags(tr, flags, out.fxMoved)) out.wrote = true;
+    model.releaseSnapshotFlags(guid);
 
-    // Unconditional, even when every write above was elided: the snapshot is consumed
+    // Unconditional, even when every write above was elided: the record is consumed
     // here, so this apply changed state and is not repeatable — and `wrote`, whose one
     // reader asks exactly that, would be a lie at false. NOT a claim about what the
-    // undo record holds: the block never carries the snapshot either way, that being
+    // undo record holds: the block never carries the record either way, that being
     // model state persisted after Undo_EndBlock2 (src/shell/view/CLAUDE.md).
-    model.clearSnapshot(guid);
     out.wrote = true;
     return out;
 }