CPU: IRQ and reset interrupt handlers missing proper cycle timing

## 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.

## References

- [CPU interrupts](https://www.nesdev.org/wiki/CPU_interrupts)