Closing a parent operation leaves the children closed with a minus (-) sign

[jond01]

Describe the bug
When there is a nested circuit - an operation within an operation, and both are open, closing the top operation keeps the inner one semi-open.
After reopening the top operation, the inner one is with a minus sign (-) - as an open operation, but it is actually closed.

To Reproduce
Steps to reproduce the behavior:

1. Open the example in the repository, also here:
   https://observablehq.com/@anpaz/quantum?ui=classic
   Specifically, focus on the last example (Grover search).
2. Click on the plus (+) of the first "GroverIteration (Oracle)" operation.
3. Keep the previous operation open and close the topmost "GroverSearch" operation.
4. Open the top operation. The previously opened operation is closed but presented with a minus (-).

Expected behavior
I would expect one of the two:

1. Closing with children reset: closing a parent (or a grandparent) closes all its children and indirect grand-children. Reopening the parent appropriately presents the children closed with a (+) sign.
2. Closing with memory: when closing and reopening a parent operation, the previous state of its children is kept intact. In the above example, "GroverIteration (Oracle)" should be visually open at step 4.

Screenshots

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Edit:
This issue is connected to #17.