The vessel DivIcon was rebuilt on every render. While a simulation runs the map
re-renders ~20 Hz, so Leaflet replaced each marker's DOM element every ~50 ms —
a click's mousedown and mouseup landed on different elements and the click was
swallowed, so the vessel panel only opened when stopped. Memoize the icon on the
rounded heading + selection so the element is stable; clicks (and switching
between vessels) now work at any point during the run. Verified in-browser: panel
opens mid-run with live telemetry.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
