Adds DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES=false (required by PROTOCOL.md) and explicit TypeReference<List<ExecutionChunk>> for array parsing. Without this, batched chunks from ChunkedExporter (2+ chunks in a JSON array) were silently rejected, causing final:true chunks to be lost and all exchanges to go stale. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>