Replaces the bundled percentage-keyframe model with per-property-group
tweens. Each studio operation creates/edits only its own group's tween:
drag → position, resize → scale/size, rotate → rotation.

Includes off-screen element indicators with drag-to-move, unclipped
overlay for off-screen interaction, gesture recording replacement,
and all 6 root cause foundation fixes from the keyframe trace
investigation.