orientation-to-valueaxis.md

layerchart	major

breaking(Chart): Remove isVertical from ChartState, add valueAxis prop to Chart

ChartState.isVertical has been removed in favor of ChartState.valueAxis ('x' | 'y'), which explicitly defines which axis represents the value (dependent variable).

Simplified charts (BarChart, LineChart, AreaChart, ScatterChart) still accept the orientation prop as before — each chart maps it to the correct valueAxis internally. The <Chart> component itself now uses valueAxis directly, since orientation is ambiguous at that level (a "vertical" BarChart has valueAxis="y" while a "vertical" LineChart has valueAxis="x").

When accessing chart state:

- if (chartContext.isVertical) { ... }
+ if (chartContext.valueAxis === 'y') { ... }

When using <Chart> directly (not simplified charts):

- <Chart ...>
+ <Chart valueAxis="x" ...>