test: add reproducible FreeCAD golden oracle

fixtures/freecad-golden/scenarios/part-cone.json

@@ -0,0 +1,16 @@
+{
+  "schemaVersion": 1,
+  "id": "part-cone",
+  "category": "Part",
+  "description": "Truncated cone with radii 5 and 2 mm and height 10 mm",
+  "operation": { "type": "cone", "radius1": 5, "radius2": 2, "height": 10, "angle": 360 },
+  "tolerance": { "linear": 1e-7, "scalar": 1e-7 },
+  "expected": {
+    "shapeType": "Solid",
+    "isNull": false,
+    "isValid": true,
+    "solids": 1,
+    "volume": 408.4070449666731,
+    "boundingBox": { "min": [-5, -5, 0], "max": [5, 5, 10] }
+  }
+}