/**
 * Whether this build is a development build, so dev-only diagnostics may throw rather than log.
 *
 * Only an explicit development signal answers yes; an unset or unrecognised flag says
 * nothing, so a bundle that defines none of the three is treated as production. The
 * probes read build-time constants rather than arguments, so a test that needs a
 * particular answer mocks this module.
 *
 * @returns `true` in development, `false` in production and when nothing says.
 * @internal
 */
export declare function isDevMode(): boolean;