/**
 * Read document metadata (YAML frontmatter for Markdown, top-level keys for other formats).
 *
 * @param projectRoot - Trusted project root.
 * @param filePath - Project-root-relative file path.
 * @returns Frontmatter as key-value record, or null if absent.
 */
export declare function readDocumentMetadata(projectRoot: string, filePath: string): Record<string, unknown> | null;
/**
 * Write metadata to a document, preserving existing fields not specified in the update.
 *
 * @param projectRoot - Trusted project root.
 * @param filePath - Project-root-relative file path.
 * @param metadata - Key-value pairs to set.
 * @returns Write result with hash and opId.
 */
export declare function writeDocumentMetadata(projectRoot: string, filePath: string, metadata: Record<string, unknown>): Promise<{
    hash: string;
    opId: string;
}>;
/**
 * Delete a metadata field from a document.
 *
 * @param projectRoot - Trusted project root.
 * @param filePath - Project-root-relative file path.
 * @param field - Field name to remove.
 * @returns Write result with hash and opId.
 */
export declare function deleteDocumentMetadataField(projectRoot: string, filePath: string, field: string): Promise<{
    hash: string;
    opId: string;
}>;
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