Marker contract that controls how the document's `contracts` map may be changed by coordination workflows. When `requireSectionChanges` is present and not false, workflows such as Change Workflow and Accept Change Workflow must reject raw changeset entries that directly target `/contracts`; callers must instead use structured `sectionChanges`. The purpose is reviewability and safety. Contract entries define runtime behavior, channels, handlers, policies, sections, and operations. Arbitrary low-level patches to `/contracts` are hard for humans and agents to audit. By requiring Document Section Changes, this marker forces contract edits to be grouped by section with explicit related contracts and section metadata. This marker is interpreted by the coordination change workflows, not by the Blue Language. A processor or workflow that does not support this policy should treat it according to its must-understand and contract capability rules.