ESP-IDF stores the mbedTLS stack error as a positive magnitude (it captures
-ret), so negating it before printing produced "mbedtls:-0xFFFF8100" instead
of "mbedtls:-0x7F00" for the record-buffer allocation failure. %04X is a
minimum width, so nothing masked it.
Normalisation moves into MQTTReplyFormat.h as mbedtlsErrorMagnitude() rather
than staying inline in the bridge: inline is why this survived, since the
existing test passes the already-correct magnitude straight into replyAppendf
and never exercised the caller. It accepts either sign so a later SDK storing
the real negative code still renders, and widens to int64_t before negating
because negating INT32_MIN is undefined behaviour.
MQTTReplyFormat.h also gains the stdint.h it was always missing: it compiled
only because MQTTBridge.cpp pulls stdint in via other headers, and the host
test includes the header standalone.
Replace multiple snprintf calls with a single replyAppendf function to
improve buffer management and prevent overflow. This change enhances
the readability and maintainability of the code while ensuring that
the reply buffer is handled safely across various MQTT status and
diagnostic replies.
agessaman