Define the document model and what belongs in Conderis versus the repository #270

Decide

• Document as a new item kind in the shared numbering: fields, revisions, visibility (private, organization, public), ownership.
• Hierarchy: parent page, sibling order, moving a subtree, maximum depth, cycle rules.
• Size limits and Markdown features, including links to #N items and between pages.
• Relation to memories and project instructions: when is something a page, when a memory, when an instruction?
• Boundary with the repository: documentation that must change in the same commit as the code (API contracts close to the implementation) may belong in docs/; documentation independent of a checkout (reviews, operations, decisions narrative, specs before code) belongs in Conderis. Write the rule down with examples.

Acceptance

• Worked examples for a security review, a deployment runbook and an API contract, each placed with reasons.
• Read and write access matrix consistent with the planned task visibility (#207).
• Explicit statement of what agents see in recall.