createSeriesMarkers(series, markers) attaches a NEW primitive to the series
on every call — refreshChart() called it on every 5s SSE-driven refresh, so
a modal left open accumulated one primitive per refresh (identical markers
overdraw so it looked fine, but it's an unbounded render leak on long-open
modals). v5 pattern: create the markers primitive once in openChart, mutate
it via markersApi.setMarkers(markers) on refresh. chart.remove() in
closeChart already tears the primitive down with the chart.
momentum dev
709e7a4344