The Swadge Emulator is a Windows or Linux program which is really more of a simulator, but the name 'emulator' stuck.
The Emulator does not require the ESP-IDF, and instead the files required for compilation were copied from the ESP-IDF to ./idf-inc/ and stripped down. If function prototypes, struct definitions, or any other headers in ESP-IDF change, the changes must be manually copied here.
The ./src/idf folder reimplements a few parts of the IDF. For the most part the Emulator strives to reimplement components rather than parts of the IDF.
The ./src/components folder reimplements this project's ../components folder, which has the hardware interfaces for ESP32-S2. The Emulator is compiled with the header files from the main ../components folder for consistency.