Incident page spine: number stops from pathStops, not its own index (#236)

The /incidents/[id] page kept its own stop numbering (every geocoded call,
1..N) and path length, while its MapView now numbers only movement
incidents' non-ghosted stops. A fire with 3 geocoded calls showed stops
1-3 on the spine and unnumbered dots on the map. Use the shared
pathStops()/stopNumbers(), show 'km path' only for movement incidents,
and surface the 'may be merged' flag in the header.

Legend: a plain pin is also what an older (pre-#236) pin with no recorded
precision looks like; say so instead of claiming 'Street address'.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/components/MapView.tsx

@@ -1658,7 +1658,7 @@ export default function MapView({
             <div key={p} className="flex items-center gap-2">
               <span style={{ width: 16, height: 20, display: "inline-flex", justifyContent: "center", alignItems: "center" }}
                 dangerouslySetInnerHTML={{ __html: teardropSvg(null, "major", p).replace('width="32" height="48"', 'width="13" height="20"') }} />
-              <span className="text-ink-2">{p === "rooftop" ? "Street address" : p === "interpolated" ? "Interpolated" : p === "centre" ? "Road/place centre ≈" : "Unverified (older)"}</span>
+              <span className="text-ink-2">{p === "rooftop" ? "Street address / not recorded" : p === "interpolated" ? "Interpolated" : p === "centre" ? "Road/place centre ≈" : "Unverified (older)"}</span>
             </div>
           ))}
         </div>