The spec had three inconsistent YAML formats for custom resource types
across different sections. The canonical format is defined in
docs/schema/resource_type.schema.yaml. Update spec examples to match:
- physical_or_virtual -> resource_kind (matches schema field name)
- cli_arguments -> cli_args (matches schema field name)
- allowed_parent_types -> parent_types (matches schema field name)
- checkpointable (top-level) -> capabilities.checkpoint (matches schema)
- readable/writable/sandboxable -> read/write/sandbox (matches schema)
- handler: ClassName -> handler: module:ClassName (matches schema format)
- classification -> resource_kind (fixes extensibility section)
- child_types: [{type: x}] -> child_types: [x] (matches schema items)
- document auto_discovery as the place for per-child discovery settings
Also update ResourceTypeRecord UML class diagram to match schema fields.
ISSUES CLOSED: #5622
HAL9000