Implement keyframe transitions

[jbilcke-hf]

Priority

This is a feature that is all the rage now, so I don't think we should wait 2 months to implement this.

Generally, I would say that new AI/features should be implemented in < 2 weeks time spans (à la Hugging Face and Replicate) so that we do not become too old (AI trends move fast)

Context

Some AI models support keyframe transitions (there are a lot of ComfyUI workflows to do this, with animatediff & co)

Some do it particularly well, for instance Luma Labs: https://x.com/LumaLabsAI/status/1835742817060331783

The good news that that Clapper isn't too far from being able to do this: this can be done by implementing a ClapSegmentCategory.TRANSITION resolver, that would take the shots on both ends (start and end) and gracefully merge them using the selected transition workflow (ClapWorkflowCategory.VIDEO_TRANSITION)

Solution

• add a rule when resolving a transition to grab the shots at both ends
• use the keyframing system from LumaLabs to implement it