Some ordering webs cause a service to be spawned twice / slist implementation bug.

Describe the bug Some ordering webs cause a service to be spawned twice.

LLM tracked the root cause to a broken implementation of slist::is_queued(). it returns false for the element at the tail of the queue.

To Reproduce

slist_bug.cpp repro.tar.gz

Expected behaviour victim service should not be spawned twice/victim.log should only contain a single line.