ToolField
ToolField =
FieldCommon&object|FieldCommon&object|FieldCommon&object|FieldCommon&object|FieldCommon&object|FieldCommon&object|FieldCommon&object|FieldCommon&object
One input. The kit picks the control; a tool never draws its own. The wire form is
flat: { "id": "url", "type": "text", "label": "URL", "placeholder": "https://…" }.