Allow ferrite beads without impedance_ohm to load.

Missing Z is optional, not invented. graph_build skips bad models
instead of aborting. Other inductors still require value_henries.

tests/test_inductor_specs.py

@@ -0,0 +1,107 @@
+"""Ferrite beads without Z validate; other inductors still need henries."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+from pydantic import ValidationError
+
+from backend.periscopex.graph import _load_component_models
+from backend.periscopex.models import ComponentModel, InductorSpecs
+from backend.periscopex.resolve_passives import simple_to_typed_passive_specs
+from backend.periscopex.models import SimpleComponentSpecs
+
+
+def test_ferrite_bead_without_impedance_ohm_validates():
+    specs = InductorSpecs(
+        component_subtype="passive.ferrite_bead",
+        value_formatted="120 ohm @ 100 MHz",
+        current_rating_a="3A",
+        dcr_ohms=0.03,
+    )
+    assert specs.impedance_ohm is None
+    model = ComponentModel(mpn="BLM21PG121SN1D", specs=specs)
+    assert model.specs.impedance_ohm is None
+
+
+def test_ferrite_bead_live_payload_without_z_validates():
+    model = ComponentModel.model_validate({
+        "mpn": "BLM21PG121SN1D",
+        "specs": {
+            "specs_type": "inductor",
+            "component_subtype": "passive.ferrite_bead",
+            "value_henries": 120.0,
+            "value_formatted": "120 ohm @ 100 MHz",
+            "tolerance": None,
+            "package": "0805",
+            "current_rating_a": "3A",
+            "dcr_ohms": 0.03,
+        },
+    })
+    assert model.specs.impedance_ohm is None
+    assert model.specs.current_rating_a == "3A"
+    assert model.specs.dcr_ohms == 0.03
+
+
+def test_ferrite_bead_with_impedance_ohm_still_ok():
+    specs = InductorSpecs(
+        component_subtype="passive.ferrite_bead",
+        value_formatted="120 ohm @ 100 MHz",
+        impedance_ohm=120.0,
+        current_rating_a="3A",
+        dcr_ohms=0.03,
+    )
+    assert specs.impedance_ohm == 120.0
+
+
+def test_inductor_still_requires_value_henries():
+    with pytest.raises(ValidationError, match="inductor requires value_henries"):
+        InductorSpecs(
+            component_subtype="passive.inductor",
+            value_formatted="15nH",
+        )
+
+
+def test_load_models_bead_without_z_does_not_raise(tmp_path: Path):
+    payload = {
+        "mpn": "BLM21PG121SN1D",
+        "specs": {
+            "specs_type": "inductor",
+            "component_subtype": "passive.ferrite_bead",
+            "value_formatted": "FB",
+            "current_rating_a": "3A",
+            "dcr_ohms": 0.03,
+        },
+    }
+    (tmp_path / "BLM21PG121SN1D.json").write_text(json.dumps(payload) + "\n")
+    loaded = _load_component_models(tmp_path)
+    assert "BLM21PG121SN1D" in loaded
+    assert loaded["BLM21PG121SN1D"].impedance_ohm is None
+
+
+def test_load_models_skips_inductor_missing_henries(tmp_path: Path):
+    bad = {
+        "mpn": "LQW-BAD",
+        "specs": {
+            "specs_type": "inductor",
+            "component_subtype": "passive.inductor",
+            "value_formatted": "x",
+        },
+    }
+    (tmp_path / "LQW-BAD.json").write_text(json.dumps(bad) + "\n")
+    loaded = _load_component_models(tmp_path)
+    assert loaded == {}
+
+
+def test_simple_to_typed_bead_without_z():
+    simple = SimpleComponentSpecs(
+        specs_type="passive",
+        component_subtype="passive.ferrite_bead",
+        values={"current_rating_a": "3A", "dcr_ohms": 0.03},
+    )
+    specs = simple_to_typed_passive_specs(simple)
+    assert specs.specs_type == "inductor"
+    assert specs.impedance_ohm is None
+    assert specs.dcr_ohms == 0.03