Prefix/suffix trimmed first; adjacent deletes and inserts read as one Replace;
beyond 3,000 edits (two texts sharing almost nothing) the middle is one Replace
instead of gigabytes of trace. Mutation-checked: a wrong tie-break, missing
replace coalescing, wrong suffix accounting and a punctuation-bearing key each
turn tests red.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
