SendInput declared its parameter as Span<INPUT>, which cannot be marshalled
(MarshalDirectiveException) — the first keyboard/mouse output threw on the
serial read thread and killed the link. Pass a blittable INPUT[] instead;
add a regression test.
Also: defend the runtime so a faulty output sink can never tear down the
serial link (output is best-effort), and dim lit lamps on the first reply
from the board rather than in Start() — lamp commands sent in the first ms
after the DTR reset (on port open) are dropped before the board has booted.
Verified end-to-end against the partial RIO on COM1 (keypad types to the PC,
joystick feeds, comms stay up; lit MFD buttons come up dim).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
CydandClaude Opus 4.8
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