If Solver.explainBestScore()'s has a total score that differs from the current best score, due to score corruption, throw a score corruption exception that says run with FULL_ASSERT or NON_INTRUSIVE_FULL_ASSERT.

Reqs:

• solve() behavior must not change. Do not end with a from-scratch calculation because that is too expensive in real-time planning.
• the logic only applies on explainBestScore()