Separate correlation history from current ownership

Keep the full bounded message history for latest-conversation safety, but let only currently eligible owners compete when selecting a reply target. Otherwise, an old human-owned case can make an explicit reply look ambiguous even when exactly one current automated case matches. First reject reclamation when the latest accepted conversation is no longer automation-owned; then filter matching candidates to current unassigned automation work; finally require an exact single semantic match. Generic, mixed, negated, or duplicate matches should still fail closed.

Applies when: one sender can have several concurrent asynchronous support cases. Keywords: inbound reply correlation ownership stale issue ambiguity exact match