Function load_failure_reason 

pub fn load_failure_reason(err: &CoreError) -> &'static str

Classify a bundle load/reload error into a stable reason label for the hoike_bundle_load_failures_total counter. Anti-rollback and continuity violations are the operationally interesting cases; everything else collapses to coarse buckets. Always available (no metrics dep) so call sites can classify even in the default build.