gizmo controls (#11274)

## Summary
Add Gizmo transform controls to load3d

- Remove automatic model normalization (scale + center) on load; models
now appear at their original transform. The previous auto-normalization
conflicted with gizmo controls — applying scale/position on load made it
impossible to track and reset the user's intentional transform edits vs.
the system's normalization
- Add a manual Fit to Viewer button that performs the same normalization
on demand, giving users explicit control
- Add Gizmo Controls (translate/rotate) for interactive model
manipulation with full state persistence across node properties, viewer
dialog, and model reloads
- Gizmo transform state is excluded from scene capture and recording to
keep outputs clean

## Motivation
The gizmo system is a prerequisite for these potential features:
- Custom cameras — user-placed cameras in the scene need transform
gizmos for precise positioning and orientation
- Custom lights — scene lighting setup requires the ability to
interactively position and aim light sources
- Multi-object scene composition — positioning multiple models relative
to each other requires per-object transform controls
- Pose editor — skeletal pose editing depends on the same transform
infrastructure to manipulate individual bones/joints

Auto-normalization was removed because it silently mutated model
transforms on load, making it impossible to distinguish between the
original model pose and user edits. This broke gizmo reset (which needs
to know the "clean" state) and would corrupt round-trip transform
persistence.

## Screenshots (if applicable)

https://github.com/user-attachments/assets/621ea559-d7c8-4c5a-a727-98e6a4130b66

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-11274-gizmo-controls-3436d73d365081c38357c2d58e49c558)
by [Unito](https://www.unito.io)

src/services/load3dService.ts

@@ -216,6 +216,9 @@ class Load3dService {
   async copyLoad3dState(source: Load3d, target: Load3d) {
     const sourceModel = source.modelManager.currentModel
 
+    const gizmoWasEnabled = target.getGizmoManager().isEnabled()
+    target.getGizmoManager().detach()
+
     if (sourceModel) {
       // Remove existing model from target scene before adding new one
       const existingModel = target.getModelManager().currentModel
@@ -256,6 +259,36 @@ class Load3dService {
             source.getModelManager().appliedTexture
         }
 
+        const sourceInitial = source.getGizmoManager().getInitialTransform()
+        modelClone.position.set(
+          sourceInitial.position.x,
+          sourceInitial.position.y,
+          sourceInitial.position.z
+        )
+        modelClone.rotation.set(
+          sourceInitial.rotation.x,
+          sourceInitial.rotation.y,
+          sourceInitial.rotation.z
+        )
+        modelClone.scale.set(
+          sourceInitial.scale.x,
+          sourceInitial.scale.y,
+          sourceInitial.scale.z
+        )
+
+        target.getGizmoManager().setupForModel(modelClone)
+        const gizmoTransform = source.getGizmoTransform()
+        target.applyGizmoTransform(
+          gizmoTransform.position,
+          gizmoTransform.rotation,
+          gizmoTransform.scale
+        )
+        const shouldEnable =
+          gizmoWasEnabled || source.getGizmoManager().isEnabled()
+        if (shouldEnable) {
+          target.setGizmoEnabled(true)
+        }
+
         // Copy animation state
         if (source.hasAnimations()) {
           target.animationManager.setupModelAnimations(