bvai-dev/hbb_common — reverse-engineered prompt

I have this Rust repo with some proto files and a few examples, but there isn't a README yet. Please help me turn it into a clean shared library crate that other Rust services can use. The goal is to keep all the common message types and helper code in one place, generate Rust code from the protocol files during the build, and make the examples show how to use the library in a simple way.

Please inspect what is already here, fix anything that stops it from building, wire up the proto generation properly, and add a short README that explains what the crate is for, how to build it, how to run the examples, and how another project would depend on it. Keep the API simple and documented enough that someone lightly technical can understand it. If tests are missing, add a couple of basic ones so I know the generated messages and main helpers work.