Prevent touch events on modal panels and their backdrop from
propagating to the canvas by adding event.stopPropagation() on
panel touch listeners.
This matches the existing behavior for sidebar panels and prevents
OrbitControls from responding to touches on modal overlays.
Acceptance Criteria:
- Touch events on modal panels do not propagate to the canvas
(event.stopPropagation() on modal and backdrop touch listeners)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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