GxEPD2 polls the panel's BUSY pin for the whole refresh (up to ~1-2s),
stalling the main loop. A TX finishing in that window left the SX126x in
standby -- deaf -- until the refresh ended; packets received meanwhile could
be lost (only the latest is readable, and a later CRC failure rejects a good
one still pending). Hook GxEPD2's busy callback to finish TX / drain RX into
a small staging queue and re-arm right away, without touching dispatch/UI.
Wired only where the display driver supports it (GxEPD2: the two e-ink Solo
boards); OLED and sim builds are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>