/**
 * Shallow-merges two ECharts option objects:
 *   - Top-level keys from both are combined.
 *   - Arrays are merged by index (element-wise shallow merge, primitive override).
 *   - Plain objects are shallow-merged.
 *   - Primitives are overridden by the override value.
 *
 * Designed for the two-stage memoization pattern: first build a base option
 * object from data + theme + formatters, then call `mergeOptions(base, override)`
 * inside a second `useMemo` keyed on `[base, override]`.
 */
export declare function mergeOptions<T extends Record<string, unknown>>(base: T, override?: Partial<T>): T;