Expand ViewTransition callback props reference documentation (#8306)

* Expand ViewTransition callback props reference documentation

Document the full callback signatures with ViewTransitionInstance
and types arguments, cleanup function return values, instance
properties (group, imagePair, old, new), and per-callback behavior.

* Add usage section for imperative animations with ViewTransition callbacks

Add "Animating imperatively with callbacks" usage section with Sandpack
example showing onEnter/onExit with instance.new.animate() and cleanup
functions. Includes addTransitionType integration example.

* Fiz lint

* Fix heading IDs to use no-space format for dead link checker

The dead link checker regex expects {/*id*/} format without spaces.
Prettier reformatted these to {/* id */} which broke anchor links.

* bump CI

* rm ;

* Human Updates

* Claude Feedback