Reports a declared failure to the observation seam — onObserved plus the OBSERVED_CHANNEL_NAME channel. Task's consuming methods call this at their classification points; call it yourself only for a synchronous Result flow that never crossed a Task, so a tracing adapter sees those failures too.

import * as Failure from './failure.ts';

const Invalid = Failure.define('Invalid', (d: { field: string }) => `bad ${d.field}`);
const failure = Invalid({ field: 'email' });
Failure.observed(failure); // hand-reported: a sync Result branch a tracer should still see