[maxwellE]

• Sort the distance result on a rank computed once per label instead of a key closure that looked the label up in both maps and cloned it on every comparison.
• Walk distances over borrowed labels: the memo, cycle guard and dependency lists no longer allocate a String per visit.
• Build the hash and dep-edges maps in one bulk pass from the (sorted) entries instead of one tree search per insert.
• Skip the second hash diff and the full copy of the starting hashes when the module graph is unchanged: no module-only targets exist then.