docs: make reference metadata optional

docs/reference-verifications/README.md

@@ -10,7 +10,7 @@ Reference Verification Agent는 Build/Test Executor Agent 통과 후 generated s
 
 수행한다:
 - `reference/<model-id>/` artifact bundle과 generated solver `results.h5`를 확인한다.
-- `metadata.json`, `model.inp`, required Abaqus reference CSV files, reference CSV schema version, FESA HDF5 schema version, units, coordinate system, step/frame identity, node/element ID matching rule, output location, component naming, tolerance policy를 확인한다.
+- `model.inp`, required Abaqus reference CSV files, Reference Model Contract의 provenance, reference CSV schema version, FESA HDF5 schema version, units, coordinate system, step/frame identity, node/element ID matching rule, output location, component naming, tolerance policy를 확인한다. 선택 `metadata.json`이 존재하면 read-only로 inventory하고 계약과 대조한다.
 - FESA HDF5 dataset을 normalized row record로 읽고 Abaqus reference CSV row와 직접 비교한다.
 - comparison command가 FESA `results.h5`에서 deterministic CSV view를 materialize할 수 있지만, 이 파일은 debugging/review용 derived artifact일 뿐 reference artifact가 아니다.
 - upstream 문서가 요구할 때만 `<model-id>_strains.csv`, `<model-id>_energy_or_residual.csv`, 또는 `<model-id>_<quantity>.csv`를 추가 비교한다.
@@ -38,7 +38,6 @@ ARTIFACT CHECK -> COMPARE -> CLASSIFY -> REPORT
 
 `ARTIFACT CHECK`에서 다음 항목이 없으면 비교를 시작하지 않는다.
 
-- `metadata.json`
 - `model.inp`
 - generated solver `results.h5`
 - `reference/<model-id>/<model-id>_displacements.csv`
@@ -55,6 +54,12 @@ ARTIFACT CHECK -> COMPARE -> CLASSIFY -> REPORT
 - component naming
 - tolerance policy
 
+`metadata.json`은 필수 artifact가 아니다. 파일이 없으면 inventory에 `absent-allowed`로
+기록하고 비교를 계속한다. 파일이 존재하면 read-only로 읽어 Reference Model Contract와
+실제 input/CSV의 중복 필드를 대조한다. 충돌은 `needs-upstream-decision` 또는 적절한
+schema/provenance failure로 분류하며, 파일 부재만으로 `needs-reference-artifacts`를
+선택하지 않는다.
+
 ## 비교 대상
 
 | quantity | fesa_hdf5_dataset | reference_csv |
@@ -102,7 +107,7 @@ ARTIFACT CHECK -> COMPARE -> CLASSIFY -> REPORT
 | --- | --- | --- | --- |
 | reference_model_dir | reference/<model-id>/ | present | missing | <notes> |
 | reference_input | reference/<model-id>/model.inp | present | missing | <input summary> |
-| metadata | reference/<model-id>/metadata.json | present | missing | <provenance summary> |
+| optional_metadata | reference/<model-id>/metadata.json | present / absent-allowed / conflict | <contract cross-check summary> |
 | reference_displacements_csv | reference/<model-id>/<model-id>_displacements.csv | present | missing | <row/schema summary> |
 | reference_reactions_csv | reference/<model-id>/<model-id>_reactions.csv | present | missing | <row/schema summary> |
 | reference_internalforces_csv | reference/<model-id>/<model-id>_internalforces.csv | present | missing | <row/schema summary> |
@@ -171,7 +176,7 @@ ARTIFACT CHECK -> COMPARE -> CLASSIFY -> REPORT
 ## 품질 기준
 
 - 모든 `must` requirement의 reference-comparison 항목은 model id, compared quantity, FESA HDF5 dataset, reference CSV, tolerance에 trace되어야 한다.
-- reference artifact는 읽기 전용이다. `model.inp`, `metadata.json`, `reference/<model-id>/<model-id>_*.csv`를 수정하지 않는다.
+- reference artifact는 읽기 전용이다. `model.inp`, 존재하는 `metadata.json`, `reference/<model-id>/<model-id>_*.csv`를 수정하지 않는다.
 - FESA `results.h5`가 authoritative solver output이고 Abaqus reference CSV files가 authoritative reference result다.
 - solver debug CSV view는 행 정렬과 사람이 검토 가능한 비교 view일 뿐이며 tolerance에 맞추기 위해 후처리 보정하지 않는다.
 - stress/strain은 element id, integration point 또는 recovery location, component naming이 일치할 때만 비교한다.

docs/reference-verifications/linear-static-3d-euler-beam-reference-verification.md

@@ -23,8 +23,8 @@ B33 reference tolerance. It does not approve physics sanity or release readiness
 
 The approved B33 exception overrides the generic new-bundle inventory. The exact
 four legacy files with spaces are the complete read-only reference bundle;
-`metadata.json`, `README.md`, and a stress CSV are contractually N/A and are not
-missing artifacts.
+`metadata.json` is absent-allowed under project-wide policy, while `README.md` and a
+stress CSV are contractually N/A and are not missing artifacts.
 
 | item | exact path | status | direct audit evidence |
 | --- | --- | --- | --- |
@@ -33,7 +33,7 @@ missing artifacts.
 | displacement CSV | `reference/cantilever beam/cantilever beam displacements.csv` | present, valid | Exact 9-column CAE header; 11 unique rows; 66 finite values. |
 | reaction CSV | `reference/cantilever beam/cantilever beam reactions.csv` | present, valid | Exact 9-column CAE header; 11 unique rows; 66 finite values. |
 | elemental-force CSV | `reference/cantilever beam/cantilever beam elemental forces.csv` | present, valid | Exact 7-column CAE header; 11 unique rows; 44 finite values. |
-| legacy metadata | `reference/cantilever beam/metadata.json` | N/A | Approved design, ADR-010, I/O definition, and reference-model contract supply provenance. |
+| optional metadata | `reference/cantilever beam/metadata.json` | absent-allowed | Approved design, ADR-010, I/O definition, and reference-model contract supply provenance; absence is not a missing artifact. |
 | legacy README | `reference/cantilever beam/README.md` | N/A | Approved B33 legacy exception. |
 | reference stress CSV | N/A | N/A | Abaqus beam-stress comparison is outside the approved V0 scope. |
 | authoritative solver output | `.harness/build/reference/cantilever-beam-b33/results.h5` | present, valid | 25,336 bytes; generated by the fresh exact CTest; HDF5 schema inspected read-only with HDF5 2.1.1 utilities. |