sbplat/Minecraft-Client-Base ? reverse-engineered prompt

Build me a simple external Minecraft client base in C++ that uses JNI to inject a loader into the game and then load a client from there. I want it to support both vanilla and Forge, and I need the whole thing set up so I can build the injector and loader with CMake, then build the client separately with a batch file.

Please include the pieces needed to download and use the right mappings for a specific Minecraft version, and make it clear how the inject flow should work from starting Minecraft to running the injector and having the loader bring the client in. If there are common crash issues with JNI versions or mismatched Java versions, please make the setup and instructions account for that. Keep it practical and working, and if you need to look up current docs or JNI details online, go ahead and do that.