Function load_freshness_threshold 

pub fn load_freshness_threshold(start_dir: &str) -> i64

load_freshness_threshold(start_dir) (ADR-045): the freshness.stale_after_days from the nearest .decided/config.yaml. Defaults to 180 when there is no config, no freshness mapping, or the value is not a positive int — YAML 1.1 bools are explicitly rejected (true/false are not day counts even though bool is an int subclass in Python).