Host signals: the Orin's health on yukart/host/<signal> (source host)

Temperatures, CPU/GPU load, memory, module power, fan, WiFi/LTE/tablet
links and the UPS battery, published by svc-core's orin-status.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

schema/topics.json

@@ -22,6 +22,13 @@
       "publisher": "gnss",
       "description": "value is an object: lat, lon, alt_m, speed_kph, heading_deg, fix, satellites."
     },
+    "yukart/host/<signal>": {
+      "payload": "envelope",
+      "retained": true,
+      "rate": "1/s",
+      "publisher": "orin-status",
+      "description": "The Orin itself: temperatures, load, memory, network links, UPS battery. One topic per signal, named exactly as in signals.json (source=host)."
+    },
     "yukart/system/<service>": {
       "payload": "json",
       "retained": true,