VaporView applyState double-disposes rows of expanded groups

In the VaporView waveform webview, applyState (used for undo/redo and apply-state) calls removeVariable(visibleSignalsFlat, recursive=true). visibleSignalsFlat contains a group and its expanded children. handleRemoveVariable pushes each child once through the group's recursive expansion and again as its own entry, then disposes it twice: TypeError 'this.rowItems[i].dispose' is undefined, and later 'o.getValueAtTime'. It reproduces with any expanded group that has children. Work around it on the host side: send only top-level rows, or collapse groups before apply-state.