wait_clk() aborted on any asserted ATN, but ATN is held low for the
entire command phase by design. Reception therefore aborted on the
first poll before clocking a single bit, so the listener never decoded
the LISTEN command and always fell through to "not addressed -> IDLE".
Make the ATN abort phase-relative via IEC_RX_ATN meaning "ATN changed":
in the data phase abort when ATN asserts (C64 interrupts with a new
command); in the command phase abort when ATN releases (command
sequence finished). The check collapses to
`iec_atn_asserted() == data_phase`.
Closes#2
Generated by Clanker
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
