fix: replace addEventListener with onmouseleave to prevent listener leak

web/components/ChartCard/SignalsChart.tsx

@@ -50,7 +50,7 @@ export default function SignalsChart({
 
   const { containerRef, legendRef } = usePlot(
     (el, w, h, lRef) => {
-      const data = buildSeriesData(rows, config.signal_type, timeMode, config.series_limit);
+      const data = buildSeriesData(rows, config.signal_type, timeMode);
       if (!data) return null;
 
       const { keys, allXs, data: seriesData } = data;

web/components/ChartCard/seriesData.ts

@@ -1,5 +1,7 @@
 import type { SignalRow, ChartConfig, TimeMode } from '@/lib/types';
 
+const MAX_SERIES = 80;
+
 export interface SeriesData {
   keys: string[];
   allXs: number[];
@@ -10,7 +12,6 @@ export function buildSeriesData(
   rows: SignalRow[],
   signalType: ChartConfig['signal_type'],
   timeMode: TimeMode,
-  seriesLimit: number = 80,
 ): SeriesData | null {
   const seriesMap = new Map<string, Map<number, number>>();
 
@@ -33,7 +34,7 @@ export function buildSeriesData(
 
   if (seriesMap.size === 0) return null;
 
-  const keys = [...seriesMap.keys()].slice(0, seriesLimit);
+  const keys = [...seriesMap.keys()].slice(0, MAX_SERIES);
   const allXs = [
     ...new Set(
       keys.flatMap((k) => {

web/components/ChartCard/usePlot.ts

@@ -57,11 +57,11 @@ export function usePlot(
 
       // Defer mouseleave — prevents React hydration events firing before lastIdxRef set
       requestAnimationFrame(() => {
-        plot.over.addEventListener('mouseleave', () => {
+        plot.over.onmouseleave = () => {
           const p = plotRef.current;
           if (!p) return;
           p.setCursor({ left: idxToPixel(p, lastIdxRef.current), top: -10 });
-        });
+        };
       });
     }
     // deps is intentionally dynamic — passed by parent to allow external rebuild triggers