/**
 * THE CANONICAL BRIDGE. Compose {@link classifyUpdate} + {@link encodeTranscriptEvent}: given one raw
 * ACP `session/update` `update` object (the `params.update`), return the EXACT on-wire transcript-chunk
 * bytes a producer appends — the nwfTranscriptEvent-marker-as-key string {@link parseTranscriptEvent}
 * decodes to a typed event and {@link deriveView} folds into a message / tool card — or `null` when the
 * update carries no canonical meaning (an `ignored` classification: `plan`, an intermediate
 * `tool_call_update`, a non-text chunk, or a malformed update).
 *
 * Pure, total, and the SINGLE authoring path for the wire: no new envelope grammar, no hand-rolled
 * marker. A producer emits `acpUpdateToTranscriptChunk(update)` (skipping `null`); a consumer decodes
 * it with {@link parseTranscriptEvent}. The `@nanobpm/agentic/protocol/conformance` transcript vectors
 * pin this exact round-trip so a producer and a consumer can never diverge on the wire again.
 */
export declare function acpUpdateToTranscriptChunk(update: unknown): string | null;