A repeat of a packet the session already took, and a packet too far ahead to be
remembered, delivered no frame and so drew the superseded-write refusal again on
every send, breaking write-receipt rule 1. The refusal now applies only to the
first packet the session takes for a sequence; CultNetRudpSession::has_received
exposes that test.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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