Function planning_chain 

pub fn planning_chain(
    repo: &dyn Repo,
    class: &str,
) -> Result<Vec<ClassInfo>, HwError>

2026-09-30: The classes a plan on class reads rules and families from: its HARDWARE.toml chain, continued through the inherits of the last class’s FUSIONS.toml (a class that does not inherit gb10’s sources may still declare that it plans with gb10’s rules).