Issue #3612351: Value-aware joins must vote on the result of a structured interaction outcome

Fixes value-aware joins that stall on a structured interaction outcome. When an interaction stores a {result, comment} pair (for example the comment_operation task) into a join's collect variable, the scalar comparison never matches its approve value, so a quorum never counts the vote and the join stalls.

JoinCoordinator now collapses a collected value that is an array with a result entry to that entry, at both the join-decision and the vote-merge collection points, so every value-aware join (quorum, threshold, matching) and the merged vote list a count condition routes on handle a structured outcome; a plain scalar is unchanged.

Adds kernel coverage: the merged list unwraps a structured vote, and a quorum plugin fires on the result of a structured approval.