Constant KERNEL_SET_HASH 

pub const KERNEL_SET_HASH: &str = "ad2aa3a9570f";

2026-09-25: Hash of the generated target_ptx.rs text (content_hash in build.rs), emitted as the METRALE_KERNEL_SET_HASH rustc-env on both the compiling and the skip-stub path. Reading it here with env! ties this crate’s build to the generated file’s content.