/**
 * Duplicate-key detection for JSON text.
 *
 * `JSON.parse` resolves `{"a":1,"a":2}` to `{a: 2}` silently. For a manifest
 * that is unacceptable: two peers reading the same bytes could disagree about
 * which artifact digest a worker claimed, and a digest computed after parsing
 * would attest to only one of them. Duplicate keys are therefore rejected
 * while the text is still text.
 *
 * The scanner is a structural pass, not a full parser — it locates strings and
 * object boundaries well enough to collect key names per object, and leaves
 * every other validity question to `JSON.parse`, which runs afterwards.
 *
 * @module worker/manifest/json-scan
 */
/**
 * Report the first duplicate key in JSON text, or `undefined` when every
 * object has unique keys.
 *
 * Malformed text yields `undefined` rather than a diagnosis: this pass only
 * answers the duplicate-key question, and `JSON.parse` gives a better message
 * for everything else. Text nested deeper than
 * {@link MAX_JSON_SCAN_NESTING_DEPTH} is treated the same way — the scan
 * bails before the open-container stack can grow without bound.
 */
export declare function findDuplicateJsonKey(text: string): string | undefined;