Add ViewModeModel::reconcile(liveGuids) to prune snapshots of deleted
tracks; wire it into applyMode before planning. Keep membership so
undo-delete (same GUID) preserves the Design tag.
visibleTracks pass 1 now evaluates every node (parent or leaf) by its own
membership, so an untagged folder carrying its own FX/media shows in Arrange
(its default) as well as any mode derived from its children. Adds case-matrix
tests; updates the nested-Arrange assertion to the corrected rule.
Only capture a track's pre-park snapshot when none exists, so a re-park while
already parked no longer overwrites it with hidden-state zeros (leaves vanished
after toggling twice). Undo label now names the actual target mode.
planToggle now enumerates all leaves in the FolderTree instead of only tagged
membership entries, so untagged (Arrange-member) tracks park in Design and
restore in Arrange. applyMode calls TrackList_AdjustWindows + UpdateArrange so
changes render immediately. Correct the stale "tagged-only" invariant comments.
Register toggle/activate/tag/untag/show-both actions driving the D2
shell and D3 model; reapply saved active mode on project load via a
persist load-signal seam. Shared guidString helper; pure nextModeId
unit-tested.
daniel