Add missing signature-failure coverage for SignedExclusiveSwap

[Copilot]

PR feedback identified missing security-path coverage in SignedExclusiveSwap tests: the suite did not assert explicit reverts for expired signatures or payload/signature mismatches. This update adds focused tests for both failure modes.

• Signature validation coverage

  • Added test_revert_signature_expired to assert ISignedExclusiveSwap.SignatureExpired when meta.deadline is in the past.
  • Added test_revert_invalid_signature to assert ISignedExclusiveSwap.InvalidSignature when the signed payload differs from the payload used at execution.

• Targeted scope

  • Changes are isolated to test/extensions/SignedExclusiveSwap.t.sol.
  • No contract logic changes; this PR strengthens regression protection around signature gating behavior.

vm.expectRevert(ISignedExclusiveSwap.SignatureExpired.selector);
harness.swapSigned(
    address(signedExclusiveSwap),
    poolKey,
    params,
    meta,
    minBalanceUpdate,
    signature,
    address(this),
    address(this)
);

vm.expectRevert(ISignedExclusiveSwap.InvalidSignature.selector);
harness.swapSigned(
    address(signedExclusiveSwap),
    poolKey,
    params,
    meta,
    createPoolBalanceUpdate(-30_000, 50_000), // mismatched from signed payload
    signature,
    address(this),
    address(this)
);

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[Copilot]

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