Get query version working by storing and reading the entire canvas as before, probabl...

Get query version working by storing and reading the entire canvas as before, probably an issue with xy coordinates being used to fetch work bytes. Anyway, it's loads faster now, but loading up all 16 workers is a no-go, so that needs work. Also would be nice to reduce the canvas viewport and associated renderbuffer to a single pixel since that's all we need.