authCapture: relax refundDeadline ordering to >= for contract parity

The contract's _validatePayment uses `preApprovalExp <= authorizationExp
<= refundExp` (equal allowed). Spec was using strict `>` on the refund
side, rejecting refundDeadline === captureDeadline configs that the
contract itself accepts. Aligning to >= avoids the off-chain/on-chain
divergence; the impl change ships alongside.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: A1igator

specs/schemes/authCapture/scheme_authCapture_evm.md

@@ -160,7 +160,7 @@ The facilitator performs these checks in order:
 3. **Network match**: `payload.accepted.network === requirements.network` and format is `eip155:<chainId>`.
 4. **Extra validation**: `requirements.extra` contains all required fields (`captureAuthorizer`, `captureDeadline`, `refundDeadline`, `feeRecipient`, `minFeeBps`, `maxFeeBps`, `name`, `version`).
 5. **Method routing**: `extra.assetTransferMethod` (default `"eip3009"`) matches the payload shape.
-6. **Deadline ordering**: `refundDeadline > captureDeadline`, `captureDeadline > now + 6s`, and `payload.validBefore` (EIP-3009) / `payload.deadline` (Permit2) `<= captureDeadline`.
+6. **Deadline ordering**: `refundDeadline >= captureDeadline`, `captureDeadline > now + 6s`, and `payload.validBefore` (EIP-3009) / `payload.deadline` (Permit2) `<= captureDeadline`. Matches the contract's `preApprovalExp <= authorizationExp <= refundExp` invariant.
 7. **Time window**: `payload.deadline / validBefore > now + 6s` (not expired) and `validAfter <= now` (active, EIP-3009 only).
 8. **Spender / collector match**: `payload.to === EIP3009_TOKEN_COLLECTOR_ADDRESS` (EIP-3009) or `payload.spender === PERMIT2_TOKEN_COLLECTOR_ADDRESS` (Permit2).
 9. **Token match**: `payload.permitted.token === requirements.asset` (Permit2 only — EIP-3009 binds via signing domain).
@@ -199,7 +199,7 @@ The authCapture scheme uses the standard x402 error codes plus these scheme-spec
 | `unsupported_asset_transfer_method` | `assetTransferMethod` is not `"eip3009"` or `"permit2"`.                 |
 | `payload_method_mismatch`           | Payload shape doesn't match `assetTransferMethod`.                       |
 | `capture_deadline_expired`          | `captureDeadline <= now + 6s`.                                           |
-| `invalid_deadline_ordering`         | `refundDeadline <= captureDeadline`.                                     |
+| `invalid_deadline_ordering`         | `refundDeadline < captureDeadline`.                                      |
 | `authorization_expired`             | EIP-3009 `validBefore` (or Permit2 `deadline`) `<= now + 6s`.            |
 | `authorization_not_yet_valid`       | EIP-3009 `validAfter > now`.                                             |
 | `invalid_authCapture_signature`     | Signature verification failed.                                           |