Function resolution 

pub fn resolution(
    config: &Config,
    board: &BoardConfiguration,
    board_name: &str,
) -> CategoryResolution

Build the resolution for board.

Once per config load. The per-issue path is a lookup against the result.

The legacy reconciliation lives in BoardConfiguration::category_for, which WP01 wrote and this module does not duplicate: a board with no category_map resolves its done_column to completed and everything else to the safe default. Duplicating that fallback here is how a board ends up with two notions of its own default.