This test is still expected to fail with our current `LogContextScopeManager` implementation but there were some flaws in how we were handling the logcontext before (like pumping the reactor in a non-sentinel logcontext) This test is originally from https://github.com/element-hq/synapse/pull/18849 spawning from https://github.com/element-hq/synapse/pull/18804#discussion_r2268254424