UI: Slider Preview Component

[mihar-22]

Implement a SliderPreview primitive for showing hover/scrub preview content anchored to slider interaction state. This is separate from Tooltip and should be reusable by TimeSlider and SliderThumbnail.

Includes core logic, DOM props builder, and React/HTML implementations.

Progress

• Core (preview positioning/state)
• Core/DOM (preview props + interaction wiring)
• React (SliderPreview composition)
• HTML (media-slider-preview element)

Related

• UI: Slider Component #275 (Slider Component)
• UI: Time Slider Component #267 (Time Slider Component)
• UI: Slider Thumbnail Component #502 (Slider Thumbnail Component)

References

• Vidstack: Slider Preview
• Vidstack: Time Slider
• Media Chrome: Preview Thumbnail