Cut 1: one watermark owns ordered delivery, seeded only by the handshake.
Cut 1b: every ending drops what the session still owed; flush is bound
to its generation. Cut 1c: a Connect repeats only by its sequence;
stale data and stale Connects are handled as TCP does (challenge Ack);
an unanswered attempt retries at +window-1; the session draws its
initial sequence. Wire bytes unchanged in all four runtimes. Five Soul
passes. Public option types changed: initial_sequence is optional.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>