mit-pdos/xv6-riscv — reverse-engineered prompt

Build me a small teaching operating system like MIT xv6, written in C for RISC V, that I can run locally in QEMU. I want it to feel like a tiny Unix system that is easy to read and learn from, not a production OS.

Please include the core kernel pieces, a few simple user programs, a way to build the file system image, and a Makefile so I can just run make qemu after installing the RISC V toolchain and QEMU. Keep the code style simple and clear, with comments where they help explain the operating system ideas.

I also want basic instructions in the README for installing the needed tools, building it, running it, and troubleshooting common setup issues. If you need exact current commands for the RISC V toolchain or QEMU, look up the current docs online.