Strip FX writes from the Design View mode switch; split view.cpp into park/lanes/reconcile/tracks and add the record-scoped undo repair pass

tests/test_view_mode_model.cpp

@@ -816,11 +816,11 @@ using LiveFlags = std::map<std::string, int>;
 // Returns nothing; mutates `vm` snapshots/active mode and `live` flags in place,
 // exactly mirroring view.cpp's park then restore then setActiveMode ordering.
 //
-// Guarded, the park mirrors decidePark's three ways: a held snapshot parks
-// without recapturing, a chain that already reads parked with no snapshot is
-// REFUSED (left exactly as found), and only a clean chain is snapshotted. The one
-// `live` flag stands in for the whole park-flag-plus-FX fold the shell reads —
-// the model half of the defect is identical either way.
+// Guarded, the park recaptures only when the model holds no record — the property
+// the shell's parkTrack keeps. Its second guarded branch (a parked-looking chain
+// with no record is left alone) outlived the shell rule it mirrored and is kept
+// here only as a second unguarded-vs-guarded contrast; the model half of the defect
+// is identical either way.
 void simulateApplyMode(ViewModeModel& vm, LiveFlags& live, const FolderTree& tree,
                        const std::string& target, bool guard) {
     TogglePlan plan = vm.planToggle(tree, target);