Widens _verify_created_cards to also accept ids that are children of the
completing task in task_links. Previously we only accepted cards where
created_by matched the completing task's assignee, which was too strict
for legitimate orchestrator flows: a specifier creates a card (so
created_by=specifier, not worker), then a worker picks it up and passes
parents=[current_task] to kanban_create. The explicit link proves the
relationship and should be trusted.
Salvaged from #20022 @LeonSGP43 (full PR superseded by #20232 +
this patch; the linked-children relaxation was the portable
improvement).
6d302b340e