Documentation contract (maintainer)

The documentation set must remain:

• auditable: changes are explicit and checksum-tracked
• tiered: user vs overview vs spec vs maintainer
• accurate: contract pages match runtime behavior

Required properties

• Every markdown file under docs/ is tracked by checksum.
• docs/index.md lists every tracked file.
• Spec pages use normative language and avoid implementation noise.

What to avoid

• Duplicating the same concept across multiple pages without cross-links.
• Encoding unstable implementation details as guarantees.
• Mixing maintainer process notes into the spec.

Enforcement: tests/invariants/test_documentation_invariant.py.