mark_unobserved doesn't switch necessary children to clean

[lord]

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[lord]

should also remove from queue; if they were in the queue, i guess they were dirty?

[lord]

there's also the bug where if a node becomes non-observed because we mark its inbound observed edge as 'dirty' we won't mark upstream things as non observed. in general we have a lot of observed bugs. maybe should move more observed calculation shit into the graph.

also i think if a node is not observed, we can skip incrementing height for its children. only important bit is that observed nodes that descend from another observed node have different heights; intermediate non-observed nodes can share height with one of the observed nodes or another