Function renderApproachDiffs

src/context/approach-diff.ts:122–155

(query: string, matches: ApproachMatch[], opts: { topK?: number } = {})

 * there's only one match (nothing to diff).
 */
export function renderApproachDiffs(query: string, matches: ApproachMatch[], opts: { topK?: number } = {}): string {
  if (matches.length === 0) return `No past work on this project resembles "${query}".`;
  const top = matches.slice(0, opts.topK ?? 4);
  const ref = top[0]!;
  const lines: string[] = [`How you approached similar work before — "${query}":`, ''];

  lines.push(`★ Best match  [${tag(ref)} · ${ref.when} · ${Math.round(ref.score * 100)}% match]`);
  lines.push(`   ${head(ref.text)}`);
  const rf = fileLinks(ref.files);
  if (rf) lines.push(rf);

  if (top.length > 1) {
    lines.push('', 'How the other attempts DIFFERED from it:');
    const refFiles = new Set(ref.files ?? []);
    top.slice(1).forEach((m, i) => {
      lines.push('', `${i + 2}. [${tag(m)} · ${m.when} · ${Math.round(m.score * 100)}% match]  ${head(m.text, 100)}`);
      if (isMultiline(ref.text) && isMultiline(m.text)) {
        lines.push('   ```diff', ...lineDiff(ref.text, m.text).slice(0, 14).map(l => '   ' + l), '   ```');
      } else {
        const d = termDiff(ref.text, m.text);
        if (d.added.length) lines.push(`   + this one adds: ${d.added.join(', ')}`);
        if (d.missing.length) lines.push(`   − it lacks: ${d.missing.join(', ')}`);
        if (!d.added.length && !d.missing.length) lines.push('   ≈ same approach, different occasion');
      }
      const fl = fileLinks(m.files, refFiles);
      if (fl) lines.push(fl.replace('files:', 'files (+ = not in best match):'));
    });

    const core = commonCore(top.map(m => m.text));
    if (core.length >= 2) lines.push('', `Stable core across all ${top.length}: ${core.join(', ')} — this is how you consistently approach it here.`);
  }
  lines.push(...renderTimeline(top));
  return lines.join('\n');
}