fix(charts): stop tooltip labels breaking mid-word

`overflow-wrap: anywhere` dropped the label's min-content width to one
character, so it was the only row item that could give way to a wide
value. Charts whose legend names are short also got the narrowest
tooltip, which is where it showed worst.

Assisted-by: Claude Opus 5

frontend/src/lib/uPlotV2/components/Tooltip/components/TooltipItem/TooltipItem.module.scss

@@ -25,6 +25,7 @@
 
 .uplotTooltipItemContent {
 	width: 100%;
+	min-width: 0;
 	display: flex;
 	align-items: center;
 	gap: var(--spacing-2);
@@ -40,16 +41,24 @@
 }
 
 .uplotTooltipItemLabel {
+	min-width: 0;
+	// Not `anywhere`, which drops min-content to one character and lets a wide
+	// value squeeze the label into a mid-word break.
 	white-space: normal;
-	overflow-wrap: anywhere;
+	overflow-wrap: break-word;
+	display: -webkit-box;
+	-webkit-line-clamp: 3;
+	-webkit-box-orient: vertical;
+	overflow: hidden;
 }
 
 .uplotTooltipItemValue {
 	white-space: nowrap;
+	flex: 0 0 auto;
 }
 
 .uplotTooltipItemContentSeparator {
-	flex: 1;
+	flex: 1 1 24px;
 	border-width: 0.5px;
 	border-style: dashed;
 	min-width: 24px;

frontend/src/lib/uPlotV2/components/Tooltip/components/TooltipItem/TooltipItem.tsx

@@ -34,7 +34,9 @@ export default function TooltipItem({
 				style={{ color: item.color }}
 				data-testid={contentTestId}
 			>
-				<span className={Styles.uplotTooltipItemLabel}>{item.label}</span>
+				<span className={Styles.uplotTooltipItemLabel} title={item.label}>
+					{item.label}
+				</span>
 				<span
 					className={Styles.uplotTooltipItemContentSeparator}
 					style={{ borderColor: item.color }}

frontend/src/lib/visualization/charts/ChartWrapper/ChartWrapper.tsx

@@ -17,7 +17,8 @@ import { ChartWrapperProps } from 'lib/visualization/charts/types';
 import { useChartStacking } from 'lib/visualization/charts/ChartWrapper/useChartStacking';
 
 const TOOLTIP_WIDTH_PADDING = 120;
-const TOOLTIP_MIN_WIDTH = 300;
+// Holds a tooltip row's value column next to a legend-length label.
+const TOOLTIP_MIN_WIDTH = 360;
 
 export default function ChartWrapper({
 	legendConfig = { position: LegendPosition.BOTTOM },