Validate persistence containment shape

[sergej-koscejev]

Parent

Parent: #1

What to build

Add structural validation for persistence containment shape. This slice checks XML tree placement and required roles for roots, child nodes, properties, and references without attempting concept-specific cardinality or language semantics.

Acceptance criteria

• Root element must be <model>.
• Root nodes in a validation target are accepted only in valid root positions.
• Root nodes must not have a child role.
• Child nodes must appear under another node and must have a child role.
• property elements must appear under a node.
• ref elements must appear under a node.
• The validator does not enforce concept-specific child cardinality or language-level containment rules.
• Tests cover valid containment shape, child nodes without roles, root nodes with roles, and misplaced properties/references.

Blocked by

• Blocked by: Support file-per-root model folders and incomplete root validation #4