feat: target-ontology-adapter §7 Golden compliance fixture and tests

[deanban]

Golden YAML manifest exercising every DTO type plus the protocol-conformance compliance suite (stable hashing, model_role propagation, obligation round-trip, invalid-ref rejection, edge endpoints, vocabulary bindings, enrichment decisions, card-version flow).

Tracking: #97. Source: openspec/changes/target-ontology-adapter/tasks.md §7.

Tasks

• 7.1 golden_manifest.yaml (>=8 entities across all kinds)
• 7.2 golden_manifest_hash.txt pinned digest
• 7.3 Stable snapshot-hash compliance test
• 7.4 model_role=TARGET everywhere test
• 7.5 Obligation round-trip test
• 7.6 Invalid-ref rejection sub-fixtures (property/vocab/FK)
• 7.7 Graph-edge endpoint compliance (temporal + non-temporal)
• 7.8 Vocabulary-binding ref preservation test
• 7.9 Enrichment-decision compliance + integrity test
• 7.9a Card-version + aggregate context_card_version flow