New display-board-1408.md: pin-level definition of the board's outputs
(8 multiplexed hex digits via ICM7228B, isolated LPT LED monitor block,
no readback path) and, from the firmware disassembly, everything the RIO
puts on it: F0 boot banner, F1 test-mode banner (keypad sequence A-9-E
enters, D exits), and the sub-test displays — five live encoder-count
readouts, button test with input index, two lamp patterns, keypad test.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
