- Root cause of 'steady white': fixture on Butler port2, our data only went to port1
(port data regions are independent: port1 @0x3C, port2 @0x23C)
- show mode now mirrors pattern to both ports; SHOW_DIAG=1 gives 3s off/on blink test
- Claim now verifies AERE response and warns on failure
- Docs updated with port layout note; README updated