Signals: cam_up and vision_up (orin-status), for the app's status bar

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

schema/signals.json

@@ -724,6 +724,18 @@
       "source": "host",
       "description": "Bluetooth link to the OBD-II adapter (the ELM327 on the K-line) is up: obd-poller holds it while the ECU answers"
     },
+    "cam_up": {
+      "unit": "",
+      "type": "boolean",
+      "source": "host",
+      "description": "A USB (UVC) camera is present for svc-vision: any V4L2 device on USB"
+    },
+    "vision_up": {
+      "unit": "",
+      "type": "boolean",
+      "source": "host",
+      "description": "yukart-vision (the camera's live view) is running"
+    },
     "ups_battery_v": {
       "unit": "V",
       "type": "number",