Implement scene transitions and easings

[staging-devin-ai-integration]

Summary

Add support for scene transitions and easings to StreamKit's compositor, enabling smooth animated transitions between different pipeline states or compositions.

Motivation

Scene transitions (crossfades, wipes, slides, etc.) and easing functions are fundamental to professional media production. Currently, switching between compositions or layouts is instantaneous. Adding transitions would significantly improve production quality and enable more polished output.

Areas to Explore

• Transition types: crossfade/dissolve, wipe (directional), slide, zoom, cut, and custom shader-based transitions.
• Easing functions: linear, ease-in, ease-out, ease-in-out, cubic-bezier, and other standard easing curves.
• API design: how transitions are triggered and configured — e.g. as part of pipeline reconfiguration, explicit transition nodes, or compositor-level commands.
• Timing control: duration, delay, and synchronization with media clocks.
• Integration with the compositor: how transition state is managed alongside existing layer composition.

Scope

This is a high-level roadmap item for investigation and design. No implementation is expected initially — the goal is to evaluate approaches, define the API surface, and sketch out an architecture.