What it does
deki-json is a thin JSON-parsing package other packages pull in when they need to handle JSON at runtime (network responses, configuration blobs, etc.). On ESP32 it uses the ESP-IDF json component (cJSON); the desktop build links a comparable implementation.
The engine’s scene format does not use JSON at runtime (it is MessagePack), so the editor and core do not depend on this package. It is only on the dependency path of packages that explicitly need JSON.