refactor(telemetry): text-only list empty states, distinct p50/p95 series

- paginated-list empty prop is a plain string, no icon block
- second sparkline series drawn in dimmed color; area disabled on dual charts
- duration legend shows latest p50/p95 values

src/features/telemetry/components/charts/sparkline.tsx

@@ -17,6 +17,7 @@ interface SparklineProps {
   showArea?: boolean;
   label?: string;
   color?: string;
+  series2Color?: string;
   scale?: SparklineScale;
 }
 
@@ -27,6 +28,7 @@ export const Sparkline = ({
   showArea = false,
   label,
   color = "var(--mantine-color-anchor)",
+  series2Color = "var(--mantine-color-dimmed)",
   scale,
 }: SparklineProps) => {
   if (data.length === 0) {
@@ -42,7 +44,7 @@ export const Sparkline = ({
   const secondPath = series2?.length
     ? pointsToPath(series2, VIEW_WIDTH, height, PAD, extent)
     : null;
-  const areaPath = showArea
+  const areaPath = showArea && !secondPath
     ? `${path} L${VIEW_WIDTH - PAD},${height - PAD} L${PAD},${height - PAD} Z`
     : null;
 
@@ -74,7 +76,7 @@ export const Sparkline = ({
         <path
           d={secondPath}
           fill="none"
-          stroke={color}
+          stroke={series2Color}
           strokeWidth={2}
           strokeDasharray="4 3"
           strokeLinecap="round"