pub const OPTION_FAMILIES: &[&str];Expand description
The option families a pack step and a fragment can both declare, spelled as the pack spells them.
This is the vocabulary ScannedFragment::declared_options must use: the
double-declaration rule works by string equality against the keys a step
writes in YAML, so an engine reporting hurl’s own spelling (retry-interval,
say) would match nothing and the clash would go quiet — which is exactly the
silent last-wins proef::pack::option_declared_twice exists to refuse.
Engines fold their spellings into these (hurl’s retry-interval is retry:
one policy, and a step’s retry: sets both).
Kept in step with MacroStep::declared_options, which derives the other half
of the same comparison.