feat: export Recharts theme preset for consuming apps

Add rechartsTheme config object that maps design tokens to Recharts
component props, ensuring visual consistency without adding Recharts
as a dependency. Also export CHART_COLORS, ChartSeries, and DataPoint
types for public use. Document charting strategy in COMPONENT_GUIDE.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/design-system/composites/index.ts

@@ -41,3 +41,7 @@ export { SplitPane } from './SplitPane/SplitPane'
 export { Tabs } from './Tabs/Tabs'
 export { ToastProvider, useToast } from './Toast/Toast'
 export { TreeView } from './TreeView/TreeView'
+
+// Chart utilities for consumers using Recharts or custom charts
+export { CHART_COLORS } from './_chart-utils'
+export type { ChartSeries, DataPoint } from './_chart-utils'

src/design-system/index.ts

@@ -11,3 +11,4 @@ export { BreadcrumbProvider, useBreadcrumb } from './providers/BreadcrumbProvide
 export type { BreadcrumbItem } from './providers/BreadcrumbProvider'
 export * from './utils/hashColor'
 export * from './utils/timePresets'
+export * from './utils/rechartsTheme'

src/design-system/utils/rechartsTheme.ts

@@ -0,0 +1,71 @@
+import { CHART_COLORS } from '../composites/_chart-utils'
+
+/**
+ * Pre-configured Recharts prop objects that match the design system's
+ * chart styling. Spread these onto Recharts sub-components:
+ *
+ * ```tsx
+ * import { rechartsTheme, CHART_COLORS } from '@cameleer/design-system'
+ * import { LineChart, Line, CartesianGrid, XAxis, YAxis, Tooltip, Legend } from 'recharts'
+ *
+ * <LineChart data={data}>
+ *   <CartesianGrid {...rechartsTheme.cartesianGrid} />
+ *   <XAxis dataKey="name" {...rechartsTheme.xAxis} />
+ *   <YAxis {...rechartsTheme.yAxis} />
+ *   <Tooltip {...rechartsTheme.tooltip} />
+ *   <Legend {...rechartsTheme.legend} />
+ *   <Line stroke={CHART_COLORS[0]} strokeWidth={2} dot={false} />
+ * </LineChart>
+ * ```
+ */
+export const rechartsTheme = {
+  colors: CHART_COLORS,
+
+  cartesianGrid: {
+    stroke: 'var(--border-subtle)',
+    strokeDasharray: '3 3',
+    vertical: false,
+  },
+
+  xAxis: {
+    tick: { fontSize: 9, fontFamily: 'var(--font-mono)', fill: 'var(--text-faint)' },
+    axisLine: { stroke: 'var(--border-subtle)' },
+    tickLine: false as const,
+  },
+
+  yAxis: {
+    tick: { fontSize: 9, fontFamily: 'var(--font-mono)', fill: 'var(--text-faint)' },
+    axisLine: false as const,
+    tickLine: false as const,
+  },
+
+  tooltip: {
+    contentStyle: {
+      background: 'var(--bg-surface)',
+      border: '1px solid var(--border)',
+      borderRadius: 'var(--radius-sm)',
+      boxShadow: 'var(--shadow-md)',
+      fontSize: 11,
+      padding: '6px 10px',
+    },
+    labelStyle: {
+      color: 'var(--text-muted)',
+      fontSize: 11,
+      marginBottom: 4,
+    },
+    itemStyle: {
+      color: 'var(--text-primary)',
+      fontFamily: 'var(--font-mono)',
+      fontSize: 11,
+      padding: 0,
+    },
+    cursor: { stroke: 'var(--text-faint)' },
+  },
+
+  legend: {
+    wrapperStyle: {
+      fontSize: 11,
+      color: 'var(--text-secondary)',
+    },
+  },
+} as const