Fenrir fixes

[embhorn]

• Fix f-3626: v5 MqttClient_Publish returns invalid success

[Copilot]

Pull request overview

This PR fixes issue f-3626 by ensuring MQTT v5 broker-side rejections of QoS>0 publishes are surfaced to callers (instead of incorrectly returning success), aligning the client’s publish behavior with how other v5 “ACK-but-rejected” flows are reported.

Changes:

• Add a new return code MQTT_CODE_ERROR_PUBLISH_REJECTED for v5 QoS>0 PUBLISH rejections signaled via PUBACK/PUBREC/PUBCOMP reason codes (>= 0x80).
• Update client publish handling to (a) stop QoS2 on PUBREC rejection (no illegal PUBREL) and (b) post-check PUBACK/PUBCOMP reason codes after the wait.
• Add unit tests covering QoS1/QoS2 acceptance vs rejection cases (and a v3.1.1 guard).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
wolfmqtt/mqtt_types.h	Introduces the new MQTT_CODE_ERROR_PUBLISH_REJECTED return code.
wolfmqtt/mqtt_client.h	Updates public API docs to mention the new publish rejection code (and adds a note about the write-only path).
src/mqtt_client.c	Implements publish rejection detection for v5 PUBACK/PUBREC/PUBCOMP and adds string mapping for the new code.
tests/test_mqtt_client.c	Adds regression tests validating correct return codes and QoS2 handshake behavior on v5 rejections.
ChangeLog.md	Documents the behavior change and its implications for callers, including MT/write-only caveats.

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