Insufficient input validation in deal and round creation

The DealManager and RoundManager contracts lack adequate input validation when creating deals or rounds. For example, proposeDeal in DealManager does not enforce that the _parties array contains exactly two elements, and proposeAndSignDeal in DealManager does not verify that the proposer parameter matches _parties[0].

Although these functions use the onlyOwner modifier, we recommend adding sanity checks. These checks help catch incorrect parameters early and prevent invalid agreements when CyberCorp accidentally supplies incorrect values during deal or round creation.