cleanNetworkBufferByTTL was deleting pendingOrphans without emitting them,
causing silent data loss when a B event (network connection) expired while
A events were still waiting in the 500ms orphan delay buffer.
Fix: cleanNetworkBufferByTTL now returns []CorrelatedLog for forced orphans;
cleanExpired propagates them; ProcessEvent includes them in returned results.
TestBTTLExpiry_PurgesPendingOrphans extended to assert the orphan is actually
returned in ProcessEvent results (not just removed from internal state).
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
b47f4258fd