When a revision reaches qourum and is adopted, the state all competing sibling
revisions as `Rejected`.
However, the test suite lacked coverage for deeper proposal branches,
specifically testing that this rejection correctly cascades to the
children of those rejected siblings.
Introduces a test to simulate the scenario where a delegate eagerly
proposes a chain of revisions (a child branching off a sibling) while
others concurrently accept a competing branch.
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