feat: target-ontology-adapter §2 Target-side DTOs

[deanban]

Target-side DTO set for the target-ontology-adapter capability: descriptors, refs, entity/property/edge declarations, vocabulary bindings, terms, context cards, and per-facet completeness annotations. All DTOs are frozen and extra="forbid".

Tracking: #97. Source: openspec/changes/target-ontology-adapter/tasks.md §2.

Tasks

• 2.1 SemanticCompleteness enum
• 2.2 SemanticCompletenessAnnotations (five required facets)
• 2.3 TargetModelDescriptor
• 2.4 target_model_id kebab-case validator
• 2.5 TargetEntityRef
• 2.6 TargetPropertyRef
• 2.7 VocabularyRef (INLINE/EXTERNAL)
• 2.8 TargetPropertyDecl
• 2.9 TargetEntityDecl
• 2.10 EdgeEndpointDecl
• 2.10a subject/object endpoint fields + kind validator
• 2.10b Endpoint cross-ref validator (no TABLE_ROW endpoints)
• 2.11 Re-export TargetObligationDecl from contract
• 2.12 VocabularyBindingDecl
• 2.13 TargetTermDecl
• 2.14 TargetContextCard
• 2.15 Card validators (packaging.version.Version, length, Sema-owned card_hash)
• 2.16 Module-wide frozen=True, extra="forbid" meta-test
• 2.17 JSON round-trip tests
• 2.18 extra="forbid" rejection tests
• 2.19 Edge endpoint kind-validation tests
• 2.19a card_version validation tests
• 2.20 Identity test for TargetObligationDecl == TargetObligation