/**
 * Normalize version string.
 *
 * Rules:
 *
 * - Remove `v` prefix before semver coercion.
 * - Preserve SHA-like values as-is.
 * - Return coerced semver when possible.
 * - Return original value when coercion fails.
 *
 * @param version - Version string to normalize.
 * @returns Normalized version string or null if input is empty.
 */
export declare function normalizeVersion(version: undefined | string | null): string | null;