OKF Core — Frontmatter Contract Crate

A pure Rust leaf library that owns the single source of truth for three brain contracts: OKF frontmatter parsing/serialization, the brain knowledge graph (nodes, edges, resolution), and the state graph that drives cross-repo planning. It exists to eliminate contract drift — before this crate, bastion and mev each maintained their own copies of the same frontmatter and graph logic, which could silently diverge. Now both consume okf-core via a Cargo path dependency, so a schema change happens once and every consumer picks it up at compile time.