CPU: IRQ and reset interrupt handlers missing proper cycle timing #602
Description
Summary
doIrq() missing dummy read PPU cycles
doNonMaskableInterrupt() correctly has 2 dummy PPU steps at the start (cycles 1-2 of the interrupt sequence), but doIrq() jumps straight to pushing the return address. The PPU is 6 dots short during IRQ handling.
doResetInterrupt() incomplete
Missing:
- 3 dummy push cycles (stack pointer decrement without writing)
- I flag set to 1
- 5 of the 7 PPU step cycles (only has the 2 for vector fetch)
These affect PPU-CPU synchronization during interrupts.