Visitors can now fully interact with someone else's scene — move objects,
add shapes, edit colors, etc. The previous strict view-only mode is gone.
Save remains the only auth/ownership-gated action; its rewiring lands in
a follow-up.
Renames computeIsViewOnly to computeIsVisitingOthersScene to reflect the
remaining role (it only drives the PreviewBox today; Save-copy label and
Reset button consume it next). Drops getIsViewOnly()/useIsViewOnly()
early-returns from engine actions, drag-drop, gizmo attach, keybinds,
and the Outliner row controls. Strips !isViewOnly wrappers from chrome
in Stage3DBody so the prompt box, controls, panel, and model selector
show for everyone.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
