Address CodeRabbit review on system resources widget PR

- Render the chart tooltip via a portal so it isn't clipped by the
  card's overflow:hidden (needed to stop the chart line itself
  bleeding past its rounded corners).
- Move chartColumns' width breakpoints into a lookup table and
  memoize the computed value, instead of an inline ternary.

packages/widgets/src/system-resources/chart/common-chart.tsx

@@ -127,7 +127,12 @@ export const CommonChart = ({
             },
           }}
           tooltipAnimationDuration={200}
-          tooltipProps={tooltipProps}
+          tooltipProps={{
+            // Render via portal so the tooltip isn't clipped by the card's overflow:hidden
+            // (needed to stop the chart line itself bleeding past its rounded corners).
+            portal: typeof document !== "undefined" ? document.body : undefined,
+            ...tooltipProps,
+          }}
           withTooltip={height >= 64}
           yAxisProps={yAxisProps}
           fillOpacity={chartType === "area" ? 0.3 : undefined}