'custom:{}' (a DynamicConfigSerializer with nothing set) hits EXPECT_KEY
with a '}' and returns TOK_ERROR, so loadSerial stops there and silently
drops every property after it. Nothing follows 'custom' in NodePrefs
today, so it goes unnoticed until you add one.
Also include stdlib.h, which Arduino.h was providing on-device but not
in the native test build.
Introduced consistent preferences for external LoRa FEM RX and TX gain settings in NodePrefs. Updated companion MyMesh to apply these settings during initialization and transmission. Added unit tests to verify the round-trip serialization of these new preferences.
Michael Graff