Handle non-unique elements in Mutation Observer (jest only?)

[JRJurman]

Summary

While writing the tests for #185, it was found that sometimes the mutation observer will get a duplicate of an element (usually when it is now catching up to multiple events that happened in the app).

I believe this is something that only happens in tests, and possible a side-effect of how jest / jsdom / testing-library work.

If that isn't the case, we should update the logic here:

tram-one/src/mutation-observer.ts

Lines 90 to 102 in ce27626

	new MutationObserver((mutationList) => {
	// cleanup orphaned nodes that are no longer on the DOM
	const removedNodesInMutation = (mutation: MutationRecord) => [...mutation.removedNodes];
	const removedNodes = mutationList.flatMap(removedNodesInMutation).flatMap(childrenComponents);
	removedNodes.forEach(clearNode);
	// call new effects on any new nodes
	const addedNodesInMutation = (mutation: MutationRecord) => [...mutation.addedNodes];
	const newNodes = mutationList.flatMap(addedNodesInMutation).flatMap(childrenComponents);
	newNodes.forEach(processEffects);
	});

We should see this happening in apps after #185 and we see useStores hooks not cleaning up when they have been removed.

[JRJurman]

If this doesn't happen in apps, it is easy enough to work around in the testing, and we should avoid writing unique logic to handle it.