feat: strengthen BSP and PSP validation and handoff

skills/firmware-lowlevel-psp-development/scripts/psp/test_render_psp_handoff.py

@@ -155,6 +155,14 @@ def main() -> int:
         assert candidate["passed"] is True, candidate
         assert candidate["etunel"]["sent"] is False
 
+        without_reference = render_psp_handoff.render(
+            "NEW", "CV1841CP", "candidate", psp, None, None, None,
+            static, bsp, None, None, None, None, None, None, None,
+            [], [], [], None, False,
+        )
+        assert without_reference["passed"] is True, without_reference
+        assert without_reference["reference_psp"] == {"source": None, "commit": None}
+
         packaged = render_psp_handoff.render(
             "NEW",
             "CV1841CP",