feat(ocaml-globe): smooth camera animation (tweening)
Camera now smoothly interpolates to targets instead of snapping:
- look_at_position: starts smooth animation toward a 3D point
- animate_to: animate to specific theta/phi/distance
- snap_to: immediate jump (old behavior)
- is_animating: check if mid-tween
- Exponential decay lerp: smooth approach, never overshoots
- Tween stops when within 0.001 rad / 0.01 distance of target
- Dragging cancels any active animation
Also: camera.tween_speed (default 5.0) controls animation speed.
66 tests passing.