Preview Mesh Dual (fields overlay):
- The overlay now renders from the TWO per-mesh files (already exported every
run) as two actors in one renderer, replacing the combined-file single
actor. Per-mesh opacity finally works for real (the old path could only
apply the AVERAGE of both opacities to one merged actor).
- New color pickers (1: / 2:) next to the opacity inputs in the bar, overlay
only. Colors + opacities are pure client-side (viewerState-persisted,
re-posted on change); defaults red/blue match the old baked colors.
- Viewer (viewer_dual.html): second overlay actor; layout-aware mapper +
render helpers (mapper1Active/mapper2Active/renderActiveViews) so field
selection, colormaps, and edge toggles now work in overlay too (previously
field application only targeted the side-by-side mappers); settings apply
point size/edges/representation to both overlay actors (color stays
per-mesh). Legacy combined-file overlay path kept for old widgets; the
textured overlay still uses the combined GLB (colors don't apply to
textures).
Preview Mesh (VTK): Mode selector removed from the JS bar -- the node's own
`mode` input is the only control (bar keeps just the fullscreen button).