Pull Playground - Interactive Pattern Learning

[Pull Playground](https://pattern.flybot.sg) is an interactive SPA for learning the [lasagna-pattern](https://github.com/flybot-sg/lasagna-pattern) pull DSL. Sandbox mode evaluates patterns entirely in the browser with SCI against an in-memory store, and remote mode sends the same Transit-encoded patterns to a live server. One UI, one pull engine, two transports.