Consider moving event handling to mjolnir.js (vis.gl)?

Cosmos currently uses **d3-zoom** and **d3-drag** for pan/zoom and point drag, plus D3/DOM for click, hover, and keyboard.

One option is to **switch to the vis.gl event manager, mjolnir.js**. Deck.gl’s view controllers already use mjolnir.js, so this would align cosmos with the same event stack (luma.gl + mjolnir) and could simplify integration if cosmos and deck are used together.
