fix(delivery): classify the receiver's MessageAlreadyProcessed as idempotent success

[DylanVerstraete]

Found via last night's soak on usc-devnet: 144 deliveries, 143 succeeded, and the single Reverted was not a failure at all.

What happened

A restart replayed the delivery checkpoint and resent a message that had already been fully processed:

ERROR ❌ delivery reverted; no further retries chain_key=8
  message_id=0x635ab2e7… reason=… execution reverted, data: "0x730ac1e2635ab2e7…"

0x730ac1e2 decodes to MessageAlreadyProcessed(bytes32) — MessageReceiverBase's duplicate guard — carrying our own messageId. The delivery goal was already achieved, but the classifier only knew the Inbox duplicate guard (MessageAlreadyValidated / "Already validated"), so the receiver guard fell through to the terminal path: gas burned on the resend, a terminal ERROR logged, and deliver_tx{status=Reverted} incremented — polluting the one status that should mean a genuine failure.

Change

• revert_already_validated → revert_duplicate_delivery, now matching both guards, each three ways (revert string, decoded error name, raw 4-byte selector) since node dialects differ. All three call sites (simulate, send error, mined-and-reverted) flow through this single classifier.
• Minimal IMessageReceiver mirror in write_ability::abi, asserted against the compiled MessageReceiverBase artifact by the ABI drift gate.
• Dialect test extended with the receiver cases — including the usc-devnet revert string verbatim — and the selector pinned to [0x73, 0x0a, 0xc1, 0xe2] so a mirror edit that silently stops matching real reverts fails in CI rather than on devnet.

Verification

• cargo test --workspace — 150 tests pass, 0 failed.
• ABI gate run against a compiled asc-contracts checkout: passes, proving the mirror matches the real artifact.
• clippy -D warnings clean, fmt clean.

[cursor]

PR Summary

Low Risk
Narrow change to delivery revert classification and ABI mirroring; it reduces false terminal failures without altering auth, funding, or send semantics.

Overview
Checkpoint replay after a relayer restart could resend deliveries that had already finished on the destination. The worker only treated Inbox duplicate reverts (MessageAlreadyValidated / "Already validated") as idempotent success, so receiver duplicates (MessageReceiverBase.MessageAlreadyProcessed) were logged as terminal failures and counted as Reverted even though the message had already been processed.

The shared classifier is renamed to revert_duplicate_delivery and extended to match both guards the same way (revert string, decoded error name, and raw selector) across simulate, gas estimate, and send paths. write-ability gains a minimal IMessageReceiver mirror for that error, the ABI drift gate pins it to MessageReceiverBase, and unit tests cover the usc-devnet revert payload plus a fixed selector byte pin so mirror drift fails in CI.

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