Replace _positionEthValue() with _positionEthOnly() in FitnessEvaluator.t.sol.
The new function returns only the WETH component of each position (amount0 if
token0isWeth, else amount1), ignoring KRK token value entirely. This prevents
evolution from gaming the fitness metric by inflating KRK price through position
placement — the score now reflects actual ETH reserves only.
Also removes the now-unused FullMath import.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>