Persist recovered ferrite Z by comparing against the raw JSON.

ComponentModel validation already fills impedance from quoted ohm@freq, so snapshotting the in-memory specs skipped the write.

tests/test_inductor_specs.py

@@ -220,6 +220,30 @@ def test_bead_mpn_datasheet_pdf_fills_z(tmp_path: Path):
     assert "100" in (persisted["specs"].get("value_formatted") or "")
 
 
+def test_bead_live_json_persist_unstuffs_henries(tmp_path: Path):
+    models = tmp_path / "models"
+    models.mkdir()
+    payload = {
+        "mpn": "BLM21PG121SN1D",
+        "specs": {
+            "specs_type": "inductor",
+            "component_subtype": "passive.ferrite_bead",
+            "value_henries": 120.0,
+            "value_formatted": "120 ohm @ 100 MHz",
+            "package": "0805",
+            "current_rating_a": "3A",
+            "dcr_ohms": 0.03,
+        },
+    }
+    (models / "BLM21PG121SN1D.json").write_text(json.dumps(payload) + "\n")
+    loaded = _load_component_models(models)
+    assert loaded["BLM21PG121SN1D"].impedance_ohm == 120.0
+    assert loaded["BLM21PG121SN1D"].value_henries is None
+    persisted = json.loads((models / "BLM21PG121SN1D.json").read_text())
+    assert persisted["specs"]["impedance_ohm"] == 120.0
+    assert persisted["specs"]["value_henries"] is None
+
+
 def test_bead_mpn_datasheet_pdf_without_z_does_not_invent(tmp_path: Path):
     models = tmp_path / "models"
     models.mkdir()