Remove redundant permit check

[Agusx1211]

Removes:

        // Validate permitAmount exactly matches the total required amount (deposit + fee)
        // This prevents permit/approval mismatches that could cause DoS or unexpected behavior
        unchecked {
            if (permitAmount != amount + feeAmount) revert PermitAmountMismatch();
        }

introduced on #62, the constraint is not necessary and stops permits from being re-used, forcing 2-click user interactions.

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Update the README, remove mentions to non-existent functionality and update intent and function definitions.

[ScreamingHawk]

LGTM

Confirmed an excessive approval remains but is safe. All public functions on the entrypoint require the intent signature. Intent signature signers are only able to access their own pre-approvals.