Treat KiCad PNM as MPN and skip missing U* as INSUFFICIENT_EVIDENCE.

HubAudio CSV has no U13–U39 rows; those refs stay without an invented part number. IC Value fills MPN when PNM is blank. Progress no longer labels netlist-only ICs as “no MPN in BOM”.

tests/test_validation_deterministic_seed.py

@@ -77,3 +77,7 @@ async def test_deterministic_findings_seeded_and_not_reviewed(tmp_path):
     assert data["summary"]["ERROR"] >= 1
 
     assert {x["designator"] for x in data["not_reviewed"]} == {"U3", "U6"}
+    by_ref = {x["designator"]: x["reason"] for x in data["not_reviewed"]}
+    assert by_ref["U3"] == "no datasheet PDF"
+    assert by_ref["U6"].startswith("INSUFFICIENT_EVIDENCE")
+    assert "not in BOM" in by_ref["U6"]