initial: mirror of @fn_library from fn_registry

75 components + DESIGN_SYSTEM.md + sync script.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/area_chart.tsx

@@ -0,0 +1,54 @@
+import { AreaChart as MantineAreaChart } from '@mantine/charts'
+import { Paper } from '@mantine/core'
+import { type Series, getSeriesColor } from './chart_container'
+
+interface AreaChartProps {
+  data: Record<string, unknown>[]
+  xKey: string
+  yKey?: string
+  series?: Series[]
+  stacked?: boolean
+  gradient?: boolean
+  showGrid?: boolean
+  showLegend?: boolean
+  height?: number
+  xAxisFormatter?: (value: unknown) => string
+  yAxisFormatter?: (value: unknown) => string
+  valueFormatter?: (value: number) => string
+}
+
+function AreaChartComponent({
+  data, xKey, yKey, series, stacked = false, gradient = true, showGrid = true,
+  showLegend = false, height = 300, xAxisFormatter, yAxisFormatter,
+  valueFormatter = (v) => v.toLocaleString(),
+}: AreaChartProps) {
+  const chartSeries = series
+    ? series.map((s, i) => ({ name: s.key, label: s.name, color: getSeriesColor(i, s.color) }))
+    : yKey ? [{ name: yKey, label: yKey, color: getSeriesColor(0) }] : []
+
+  return (
+    <Paper p="md">
+      <MantineAreaChart
+        h={height}
+        data={data}
+        dataKey={xKey}
+        series={chartSeries}
+        type={stacked ? 'stacked' : 'default'}
+        curveType="monotone"
+        withGradient={gradient}
+        gridAxis={showGrid ? 'xy' : 'none'}
+        withLegend={showLegend}
+        withTooltip
+        valueFormatter={valueFormatter}
+        xAxisProps={xAxisFormatter ? { tickFormatter: xAxisFormatter } : undefined}
+        yAxisProps={yAxisFormatter ? { tickFormatter: yAxisFormatter } : undefined}
+      />
+    </Paper>
+  )
+}
+
+/** @deprecated Gradient is handled by Mantine's withGradient prop */
+type GradientConfig = { from: string; to: string }
+
+export const AreaChart = AreaChartComponent
+export type { AreaChartProps, GradientConfig }