Bun Rust rewrite: "codebase fails basic miri checks, allows for UB in safe rust"

A critical bug was discovered in the Bun JavaScript runtime where the `PathString::slice` function creates dangling references, allowing undefined behavior in safe Rust code. The issue stems from unsafe pointer manipulation that fails Miri (Rust's undefined behavior detector) checks, and the reporter suggests the codebase needs proper Rust expertise rather than AI-generated code to resolve such memory safety violations.