/**
 * Hit the xtralab server extension's `which`-proxy endpoint and turn the
 * response into a Set of commands that resolved to a real binary on the
 * server's `$PATH`. The frontend uses this set to filter the launcher's
 * agent cards.
 *
 * On any failure (server extension not loaded, network error, malformed
 * response) the returned Set is `null` — callers should treat that as
 * "availability unknown" and either fall back to showing all agents or
 * surface the error, depending on context.
 */
export declare function fetchAvailableCommands(commands: string[]): Promise<Set<string> | null>;