// Caption the long-term target without changing its native topology.
// Text lives inside the SVG so standalone exports retain proposal/line semantics.
export function targetCaption(html) {
  const roots = [...html.matchAll(/<svg\b[^>]*role="img"[^>]*>/g)];
  if (roots.length !== 1) throw new Error('Target caption SVG contract drift');
  const root = roots[0][0];
  const match = /viewBox="([\d. -]+)"/.exec(root);
  if (!match) throw new Error('Target caption requires viewBox');
  const [x,y,w,h] = match[1].trim().split(/\s+/).map(Number);
  const size = Math.min(26, w / 30);
  const lines = ['Long-term Target — not a six-month commitment',
    'Solid: lifecycle · Dotted: execution / governance', 'Dashed: human-controlled contributions'];
  const extra = size * 5;
  const caption = `<g id="eldorado-target-caption" aria-label="Proposed target legend">${lines.map((line,i) => `<text x="${x+20}" y="${y+h+size*(1.2+i*1.3)}" font-family="Arial, sans-serif" font-size="${size}" style="font-size:${size}px!important" class="t-primary">${line}</text>`).join('')}</g>`;
  return html.replace(root, root.replace(match[0], `viewBox="${x} ${y} ${w} ${h+extra}"`) + caption);
}