Plays a list of items (clip + percentage range) on a VideoPlayer.
Double-buffers via a second player (auto-created child incl. AudioSource
copy) and drives the screen texture through a MaterialPropertyBlock,
flipping only once the next player delivers frames - no black/freeze gap.
Editor drawer renders each item as clip row + min-max percent range slider.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
