Re-parse .kicad_pcb on PCB exam instead of stale layout_graph.

Cached layout_graph still listed stitching via-pads as component pads,
so PE-BOM-011 kept firing after the ingest fix. PCB/placement jobs now
parse the board file and refresh the cache.

tests/test_pcb_via_not_pad.py

@@ -269,3 +269,43 @@ def test_tht_solder_pads_stay_component_pads(tmp_path: Path):
     g = parse_kicad_pcb(p)
     assert [p.number for p in g.footprints["R1"].pads] == ["1", "2"]
     assert g.vias == []
+
+
+class _Ws:
+    def __init__(self, root: Path):
+        self.root = root
+
+    def local_path(self, rel: str) -> Path:
+        return self.root / rel
+
+    def _upload_file(self, rel: str) -> None:
+        return None
+
+
+def test_pcb_pipeline_reparses_stale_layout_graph(tmp_path: Path):
+    from backend.periscopex.models import LayoutFootprint, LayoutGraph, LayoutPad
+    from backend.services.pcb_pipeline import _load_layout
+
+    uploads = tmp_path / "uploads"
+    uploads.mkdir()
+    pcb = _qfn24_pcb(
+        tmp_path,
+        n_pads=24,
+        stitch_via_pads=[(26, 0.0, 0.0, "GND")],
+    )
+    (uploads / "pcb.kicad_pcb").write_text(pcb.read_text())
+    stale = LayoutGraph(
+        footprints={
+            "U1": LayoutFootprint(
+                reference="U1",
+                footprint="QFN-24",
+                x=0, y=0, layer="F.Cu",
+                pads=[LayoutPad(number=str(i), x=0, y=0, net="GND") for i in range(1, 35)],
+            ),
+        },
+    )
+    (tmp_path / "layout_graph.json").write_text(stale.model_dump_json())
+    layout = _load_layout(_Ws(tmp_path))
+    assert layout is not None
+    assert len(layout.footprints["U1"].pads) == 24
+    assert len(layout.vias) == 1