When a replacement part with a caseLockGroup is grabbed, sibling parts
sharing the same group become non-interactable and ghosted (35% opacity)
until the held part is released. This implements the pylon cable choice
where the player picks either cable1 or cable2 (both valid) without
being able to grab both simultaneously.
- GrabbableObject: add disabled prop (skips interaction frame logic and
unmounts InteractableObject so it does not register with the manager)
and onGrabChange callback fired on press, release, hand grab, and hand
release. Force-releases when disabled becomes true mid-grab.
- SimpleModel: add opacity prop, traversed onto cloned mesh materials
(safe because cloneResources clones materials per instance).
- RepairObjectModel: forward ghosted prop as opacity 0.35.
- RepairRepairingStep: track heldPartByLockGroup and pass disabled +
ghosted to siblings of the currently held part.
Tom Boullay