Remove the fragile and heavy json libraries from the firmware

[caveman99]

remove JSON topics on MQTT, remove JSON Logging/Tracing, replace JSON output on webserver with simple string concatenation, since they use a fixed set of templates anyway.

The Heltec solar node still uses ArduinoJSON for god knows what in its included custom library.

[Copilot]

Pull request overview

This PR removes JSON-based features and dependencies from the firmware (MQTT JSON topics, JSON packet logging/tracing, and the internal JSON serialization library), replacing the webserver’s JSON responses with manual string construction.

Changes:

• Removed MQTT JSON uplink/downlink topics and related packet JSON serialization code paths.
• Removed SimpleJSON + MeshPacketSerializer (including nRF52 ArduinoJson serializer) and deleted the corresponding unit tests.
• Reworked webserver JSON responses in ContentHandler.cpp to build JSON strings directly; removed Portduino JSON/trace file logging config and plumbing.

Reviewed changes

Copilot reviewed 23 out of 24 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
variants/nrf52840/rak4631_eth_gw/platformio.ini	Drops nRF52 JSON build flag and ArduinoJson dependency for this variant.
test/test_meshpacket_serializer/test_serializer.cpp	Removes JSON serializer unit test runner (serializer feature removed).
test/test_meshpacket_serializer/test_helpers.h	Removes JSON serializer test helpers and JSON parsing dependency.
test/test_meshpacket_serializer/ports/test_waypoint.cpp	Removes waypoint JSON serialization tests.
test/test_meshpacket_serializer/ports/test_text_message.cpp	Removes text message JSON serialization tests.
test/test_meshpacket_serializer/ports/test_telemetry.cpp	Removes telemetry JSON serialization tests.
test/test_meshpacket_serializer/ports/test_position.cpp	Removes position JSON serialization tests.
test/test_meshpacket_serializer/ports/test_nodeinfo.cpp	Removes nodeinfo JSON serialization tests.
test/test_meshpacket_serializer/ports/test_encrypted.cpp	Removes encrypted-packet JSON serialization tests.
src/serialization/MeshPacketSerializer.h	Removes the MeshPacket JSON serializer API.
src/serialization/MeshPacketSerializer.cpp	Removes the non-nRF52 SimpleJSON-based serializer implementation.
src/serialization/MeshPacketSerializer_nRF52.cpp	Removes the nRF52 ArduinoJson-based serializer implementation.
src/serialization/JSONValue.h	Removes SimpleJSON value type (library elimination).
src/serialization/JSONValue.cpp	Removes SimpleJSON implementation.
src/serialization/JSON.h	Removes SimpleJSON parser/stringifier header.
src/serialization/JSON.cpp	Removes SimpleJSON parser/stringifier implementation.
src/RedirectablePrint.cpp	Removes JSON logging buffer sizing and Portduino trace special-casing.
src/platform/portduino/PortduinoGlue.h	Removes Portduino trace/JSON file globals and related config fields/YAML emission.
src/platform/portduino/PortduinoGlue.cpp	Removes Portduino trace/JSON file open and YAML config parsing for those options.
src/mqtt/MQTT.h	Removes JSON topic member and JSON include.
src/mqtt/MQTT.cpp	Removes JSON MQTT downlink handling, JSON subscriptions, and JSON publishes.
src/mesh/Router.cpp	Removes JSON trace logging of decoded/encrypted packets.
src/mesh/http/ContentHandler.cpp	Replaces SimpleJSON usage with hand-built JSON strings for web endpoints.
bin/config-dist.yaml	Removes commented-out TraceFile/JSONFile logging configuration examples.

[jp-bennett]

I would like to retain the JSON capabilities on Meshtasticd, if possible. Ideally in a simplified form.

[caveman99]

So the JSON logging in debug trace? And packet content logging?

[jp-bennett]

So the JSON logging in debug trace? And packet content logging?

Yes exactly. I know of at least one professional user of the JSON dump to file.