- Dual / Multi / VTK preview: the control bar now sits BETWEEN the canvas and
the info panel (canvas on top, controls below), matching the batch node's
nav bar. Border flipped bottom->top to suit the new position.
- Preview Mesh Dual: Mode selector removed from the bar -- the node's own
`mode` input widget is the only mode control (same policy as Preview Mesh
VTK). Bar keeps Layout, per-mesh color/opacity (overlay), and fullscreen.