Add new players chart

[tudddorrr]

No description provided.

[claude]

PR Review: Add new players chart

Overall this is clean work - the component decomposition is solid, the SWR pattern is consistent with the codebase, and the ChartTooltip → EventChartTooltip rename is handled correctly everywhere.

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🔵 Minor Issues

1. No loading indicator in BarChartCard

When loading=true and data is empty (initial fetch), the component renders nothing - no spinner, no skeleton. The empty message is correctly hidden, but there is no visual feedback to the user.

// BarChartCard.tsx
{!loading && data.length === 0 &&
  <p>{emptyMessage}</p>
}

// data.length > 0 check renders chart, but nothing renders during initial load

Consider adding a loading state (skeleton or spinner) so the card area does not appear blank during the first fetch.

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2. Positive change values lack a + prefix

In NewPlayersChart.tsx, the percentage display shows -5.0% for negative change but 5.0% (no sign) for positive, making it visually asymmetric:

{(change * 100).toFixed(1)}%

A small fix makes it unambiguous:

{change > 0 ? `+${(change * 100).toFixed(1)}` : (change * 100).toFixed(1)}%

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3. No tests for new components

BarChartCard, BarChartTooltip, and NewPlayersChart have no test files. The renamed EventChartTooltip has tests, so there is a precedent. At minimum, BarChartTooltip (which has conditional rendering and a formatter callback) would benefit from unit tests consistent with the existing chart test pattern.