duel/v4 package

Package duel implements the first slice of Splash Play I, the Duel, settled from r/splash/beacon instead of a two-party commit-reveal (SPEC-09-duel-beacon.md v1.0, ../../../../SPEC-09-duel-beacon.md).

TEMPORARY NAME. "duel" is scratch space, built beside the LIVE r/splash/arcade/duel so that realm keeps working while this one is proven. The two are swapped in one commit once this one is ready, and the deploy path is decided then (SPEC-09 is silent on it on purpose). Nothing here should be linked to, or depended on, from outside this directory.

THIS SLICE IS Post, Cancel, Accept AND THE ROUND PIN. No Resolve — that is slice 2 (SPEC-09 §3 describes the whole lifecycle; the part after Accept is not built yet). A duel created here therefore has no payout path: it exists so the pin itself, SPEC-09's "only subtle part" (§3.1), can be built and proved on its own before anything is wired to money leaving the realm.

WHY COMMIT-REVEAL IS GONE RATHER THAN CARRIED OVER (SPEC-09 §1). The old duel moved OFF the beacon on 2026-09-30 because Accept needed an UPPER bound on drand's head ("round R is not signed yet"), and no arithmetic over a RELAYED round could ever establish one: a signature proves a round EXISTS (a lower bound), and the absence of one is not provable on chain, because withholding a relay is free and invisible. beacon.CurrentRound(), added 2026-10-08, derives drand's round from the BLOCK'S OWN CLOCK instead — no relayer in the path — so that upper bound now exists, and the whole reason commit-reveal's complexity existed is gone with it. What carries over is not the lifecycle but four audit findings about THIS REALM'S OWN escrow and money handling that were never specific to commit-reveal (SPEC-09 §8): rejectAttachedCoin and requireUserCall below, no transfer destination ever being a caller-supplied argument, and (for later slices) one clock/one derived value and no sentinel field standing in for a height.

THE STAKE IS WRAPPED GNOT, exactly as in r/splash/arcade/duel: this realm escrows gno.land/r/gnoland/wugnot and touches no other token.

NO Resolved, NO Winner, NO Secret, NO Nonce, NO NonceRevealedAt, NO TakerCommit, AND NO DEADLINE OF ANY KIND IN THIS SLICE'S STATE (SPEC-09 §4, §8). Resolve (slice 2) pays and deletes a duel in one call, so a resolved duel will never exist to be recorded; there is nothing here for a sentinel "never happened yet" value to be confused with a real height.