fix(view): derive parent/folder visibility on mode toggle

applyMode now drives B_SHOWINTCP/B_SHOWINMIXER for every parent node
from visibleTracks(tree, targetMode); parents are never parked. Adds
restoreFxOffline by-index remap hazard note.

src/view.h

@@ -40,7 +40,10 @@ namespace reasampler {
 //      per-FX offline loop from TrackFX_GetCount, which the pure plan leaves empty).
 //   4. For each track to RESTORE: applies the plan's snapshot-sourced flag + per-FX
 //      offline writes verbatim.
-//   5. Sets the model's active mode to `targetModeId`.
+//   5. For each PARENT (folder) node: drives B_SHOWINTCP / B_SHOWINMIXER to 1 if the
+//      parent is in model.visibleTracks(tree, targetModeId), else 0 — derived from
+//      membership, never parked/snapshotted. Only the two visibility flags.
+//   6. Sets the model's active mode to `targetModeId`.
 // All track mutations are wrapped in Undo_BeginBlock2 / Undo_EndBlock2.
 //
 // Returns false (no mutation, active mode unchanged) if `targetModeId` is not a