test(core): add HRM-style architecture test case

tests/test_model_support.py

@@ -34,3 +34,17 @@ def test_model_support_rejects_non_eager_attention() -> None:
 
     assert support.supports_attribution is False
     assert "eager" in (support.reason or "")
+
+
+def test_model_support_accepts_hrm_layout() -> None:
+    layer = SimpleNamespace(attention=object())
+    model = SimpleNamespace(
+        model=SimpleNamespace(h_stack=SimpleNamespace(layers=[layer, layer])),
+        config=SimpleNamespace(_attn_implementation="eager"),
+    )
+
+    support = describe_model_support(model)
+
+    assert support.supports_attribution is True
+    assert support.layer_path == "model.h_stack.layers"
+    assert support.attention_attr == "attention"