Refactor Smart Filter

I'm truly sorry this isn't more granular commits.

This MR redesigns Smart Filter (aka Smart Start, aka Fancy LLM-Backed Filter Creation, etc.) so that it occupies a more prominent place atop Explore, outside of a dropdown.

It will only really work in conjunction with its sibling MR in Torque: torque!98 (merged)

Affects ots/llm/meta#42 (closed)