V3 deterministic document-to-Markdown capability pack. By-value connector composition (service_kind=cli, no separate ingredient): the local markitdown CLI converts one source document into Markdown via the document.to_markdown catalog operation. This is a lighter alternative to docling for simple office/document inputs. Write-tier but approval=never: markitdown writes only to an engine-managed throwaway output dir and the Markdown is captured as result.file_ref; source bytes and converted text never flow through op-step stdout values. Requires markitdown on PATH (Python environments: pip install markitdown==0.1.3 or a compatible installed CLI). Local and no-egress; Document Intelligence and plugin flags are not exposed.