V1.8: 25-Aug-2026 by wavemotion-dave
- Improved ADC/SBC to include the carry flag in the Overflow checks.
- Improved green artifacting so Galactic Attack (and probably some others) looks more correct.
- Improved PIA interrupt disable handling to clear the pending interrupt line.
- Improved unmapped IO handling to return last bus value for better accuracy.
- Improved interrupt handling for Cart for improved accuracy.
- Minor refactor and cleanup as time permitted.