Apply GH-DEC-2026-017: INTENT.md governs, layer.yaml is derived, no version

Remove standard_version from layer.yaml and the INTENT.md frontmatter (A12),
mark layer.yaml derived: true / derived_from: INTENT.md (A11), and change the
conformance checker and its tests in the same commit so the conforming
declaration does not fail as malformed.

The checker now requires the INTENT.md layer: key, rejects standard_version
in either form, checks the layer against the closed four-token vocabulary
(A9), and reports a layer/role disagreement between the two forms after an
ASCII case-fold. Nothing is re-spelled: INTENT.md keeps Engine/PIP and
layer.yaml keeps engine/pip. pep-stance.yaml and pip-claims.yaml keep their
standard_version; neither is a layer declaration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 63291@bnt-lap001
Assistant-Session: 8bd77868-ca68-4f49-bb1e-d539ecc0d703

tests/test_layer_conformance.py

@@ -24,7 +24,8 @@ def test_layer_yaml_declares_engine_pip():
     assert data["repository"] == "tenant-engine"
     assert data["layer"] == "engine"
     assert data["role"] == "pip"
-    assert data["standard_version"] == "0.7"
+    assert data["derived"] is True
+    assert data["derived_from"] == "INTENT.md"
     assert data["tooling_contacts"] == []
     assert data["pep_stance"] == "pep-stance.yaml"
     assert data["pip_claims"] == "pip-claims.yaml"
@@ -35,11 +36,48 @@ def test_layer_yaml_declares_engine_pip():
     assert "state-hub-work-records" in ids
 
 
+def _intent() -> dict:
+    return yaml.safe_load((ROOT / "INTENT.md").read_text().split("---", 2)[1])
+
+
+def _fold(value: object) -> str:
+    return str(value).translate(str.maketrans("ABCDEFGHIJKLMNOPQRSTUVWXYZ",
+                                              "abcdefghijklmnopqrstuvwxyz"))
+
+
 def test_intent_frontmatter_agrees_with_layer_yaml():
-    intent = yaml.safe_load((ROOT / "INTENT.md").read_text().split("---", 2)[1])
+    """A11/A9: the derived form agrees with the governing one after a case-fold.
+
+    A fold, not an equality: INTENT.md says Engine and layer.yaml says engine,
+    and neither is re-spelled. A real divergence still fails.
+    """
+    intent = _intent()
     decl = yaml.safe_load((ROOT / "layer.yaml").read_text())
-    assert str(intent["layer"]).lower() == str(decl["layer"]).lower()
-    assert str(intent["role"]).lower() == str(decl["role"]).lower()
+    assert _fold(intent["layer"]) == _fold(decl["layer"])
+    assert _fold(intent["role"]) == _fold(decl["role"])
+    assert _fold(intent["layer"]) in {"taxonomy", "tooling", "engine", "staff"}
+
+
+def test_no_declaration_carries_a_standard_version():
+    """GH-DEC-2026-017 / A12: neither form carries a standard version."""
+    assert "standard_version" not in yaml.safe_load((ROOT / "layer.yaml").read_text())
+    assert "standard_version" not in _intent()
+
+
+def test_checker_rejects_a_divergence_that_survives_the_fold(tmp_path, monkeypatch):
+    spec = importlib.util.spec_from_file_location("check_layer_conformance", SCRIPT)
+    module = importlib.util.module_from_spec(spec)
+    assert spec.loader is not None
+    spec.loader.exec_module(module)
+    fake = tmp_path / "INTENT.md"
+    fake.write_text("---\nlayer: Staff\nrole: PIP\n---\n")
+    monkeypatch.setattr(module, "INTENT", fake)
+    try:
+        module.intent_frontmatter()
+    except SystemExit as exc:
+        assert exc.code == 2
+    else:  # pragma: no cover
+        raise AssertionError("a Staff INTENT.md must not pass as Engine")
 
 
 def test_checker_passes_on_the_real_tree():