add Sideboard Reset option please

When sideboarding, if you completely mess up, there is no option to reset back to previous configuration.

Even waiting out the timer and not submitting doesn't work. (I had pressed new so there was nothing visable in maindeck at the end of sideboarding, when the game started it didn't reset to last submitted option, but instead had a random 40 cards in my library.)

Running out of time during sideboarding should leave your last submitted configuration, so a half-done hodgepodge.

Start by tracing the sideboarding state and timeout handling in the Java game and client code. Compare the last submitted deck with the temporary sideboard configuration, then verify that a reset and timer expiry preserve the submitted configuration rather than producing an invalid deck. No file or test is named, so locating the relevant entry points is part of the work.

Written by the indexing model from the issue text.