fix(simulation): accept ROS multi-document samples

simulation/s0/build_evidence_manifest.py

@@ -47,10 +47,14 @@ def _load_json(path: Path) -> dict[str, Any]:
 
 
 def _load_yaml(path: Path) -> dict[str, Any]:
-    loaded = yaml.safe_load(path.read_text(encoding="utf-8"))
-    if not isinstance(loaded, dict):
+    documents = [
+        document
+        for document in yaml.safe_load_all(path.read_text(encoding="utf-8"))
+        if document is not None
+    ]
+    if len(documents) != 1 or not isinstance(documents[0], dict):
         raise EvidenceError(f"expected a YAML mapping: {path}")
-    return loaded
+    return documents[0]
 
 
 def _result_env(path: Path) -> dict[str, str]: