Add signal layer transform updated

[tarcila]

This PR introduces a split of signalLayerUpdated into:

• signalLayerStructureUpdated (for scenegraph topological changes)
• signalLayerTransformUpdated (for transform node updates)

This helps splitting the RenderIndex behavior and split the work into two phases:

• ANARI Objects construction, including Instances
• Instances transform update only, for smoother animations

Also exposes the Ensight importer to Lua

[Copilot]

Pull request overview

This PR splits the signalLayerUpdated/signalLayerChange signal into two distinct signals: signalLayerStructureChanged (for scenegraph topological changes) and signalLayerTransformChanged (for transform-only updates). This enables an optimized rendering path for smooth animations, where only ANARI instance transforms are updated without rebuilding the full scene. It also introduces a new TransformsToAnariVisitor to handle the transform-only update path, and exposes the EnSight importer to Lua scripting.

Changes:

• Splits signalLayerUpdated/signalLayerChange into signalLayerStructureChanged and signalLayerTransformChanged throughout all subsystems (rendering index, UI, network, serialization, scripting)
• Adds new TransformsToAnariVisitor for lightweight per-frame transform updates, and refactors RenderToAnariObjectsVisitor to not set transforms (delegated to the new visitor)
• Exposes import_ENSIGHT and Animation::setAsTransformSteps to Lua scripting

Reviewed changes

Copilot reviewed 25 out of 26 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
UpdateDelegate.hpp / .cpp	Splits signalLayerUpdated into two virtual methods in the base delegate interface
Scene.hpp / .cpp	Adds signalLayerStructureChanged and signalLayerTransformChanged methods, updates internal callers
RenderIndex.hpp / .cpp	Provides default no-op implementations for the two new virtual signals
RenderIndexAllLayers.hpp / .cpp	Implements the two new signals; adds syncLayerTransforms using the new visitor
TransformsToAnariVisitor.hpp	New visitor that only updates ANARI instance transforms (for the lightweight path)
RenderToAnariObjectsVisitor.hpp	Removes transform-setting logic (now handled by TransformsToAnariVisitor)
Animation.cpp	Uses signalLayerTransformChanged for animated transform updates
NetworkUpdateDelegate.hpp / .cpp	Implements both new signals (both still transfer the full layer over network)
CoreBindings.cpp	Updates Lua binding; adds setAsTransformSteps to the Animation Lua API
IOBindings.cpp	Exposes import_ENSIGHT to Lua
UI files (ObjectEditor, LayerTree, BaseViewport, IsosurfaceEditor, ImportFileDialog)	Updates call sites to appropriate signal
Other files (World.cpp, TransferLayer.cpp, serialization, import_GLTF, InstancingControls)	Updates call sites to signalLayerStructureChanged

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[jeffamstutz]

LGTM, thanks!