Gate finding C01.r1.2c [High]: the hand-back added for failed candidates
also ran in the post-install exception/cancel branches. After a successful
secondary install (or a primary publish) the predecessor already forwards
to the new adapter; if the task was cancelled during redelivery (gateway
teardown cancels secondary reconnect tasks) the hand-back linked the new
adapter back to the predecessor, and any hold - e.g. the disconnect()
teardown salvage - ping-ponged between the two until RecursionError.
Break the cycle at both ends: adopt_held_inbound clears the adopter's own
successor link (it owns the queue again), and the runner skips the
hand-back when the adapter is the one installed in its slot. Covered by a
cancel-after-install row on the secondary hand-back test.
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