Add device contract fixture

Author: mdheller

examples/contracts/device.local.json

@@ -0,0 +1,9 @@
+{
+  "schema": "sourceos.device-record/v1alpha1",
+  "device_id": "device:local",
+  "display_name": "Local SourceOS Device",
+  "trust_level": "local",
+  "device_state": "trusted",
+  "created_at": "2026-05-05T00:00:00Z",
+  "revoked_at": null
+}