Function map_to_heading 

pub fn map_to_heading(
    groups: &[FunctionalGroup],
    organic_class: &OrganicInorganic,
) -> HeadingHint

Derive an HS chapter / heading hint from functional group analysis.

Arguments

• groups — functional groups detected by detect_functional_groups.
• organic_class — result of classify_organic.

Returns

The first matching entry in the priority table, or a Chapter-28/29 generic fallback if no specific match is found.