AmqpReplyInboxContractTest is the one contract-group class CI actually
runs, and it never asserted on ack()'s return value at all — so the
exact defect this ticket fixes (reporting success for an ack that
removed nothing) was unpinned in the adapter fleetd runs live.
Add ackReportsHitVsMissAgainstARealBroker: a msgId never held for an
owned target returns false without throwing, a real held reply returns
true and is removed, and acking the same msgId again returns false.
Ran against both broker modes the class supports: Testcontainers
(AMQP_URI unset) and an external broker via AMQP_URI (the CI shape,
using a disposable container — not the shared local LavinMQ instance).
ReplyInbox.ack now returns boolean (true = removed, false = nothing to
remove) instead of void, so FleetMcp.ack can finally tell a hit from a
miss. FleetMcp.ack returns an error when the boolean is false, naming
fleet_poll{coordId} for held peer mail, which has no route through this
call. MessageService.ackReply propagates the boolean; drainReplies keeps
ignoring it (its own javadoc already documents that loss window as
deliberate). Updated the tool schema's target description to match.
Rewrote FleetMcpTest's ack tests to publish a real message before
asserting success, and added tests for a never-queued id and a coord-id
target, both now erroring. Added boolean assertions to
InMemoryReplyInboxTest's existing ack cases.
Dai Ha