router-status: publish missing values to HA as 'unavailable'

HA renders JSON null as 'None'; map None to the string 'unavailable' for
the WAN, AP, Starlink, failover, thermal and battery payloads.

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

router-status/van-router-mqtt

@@ -99,6 +99,18 @@ DEVICE_INFO = {"identifiers": [device_id], "name": "Van Router", "manufacturer":
 WAN_NAMES = ("wifi", "starlink", "cellular")
 
 
+def mark_unavailable(obj):
+    """Copy of obj with every None replaced by 'unavailable' -- HA treats that string
+    as a missing value, whereas null renders as 'None'."""
+    if obj is None:
+        return "unavailable"
+    if isinstance(obj, dict):
+        return {k: mark_unavailable(v) for k, v in obj.items()}
+    if isinstance(obj, list):
+        return [mark_unavailable(v) for v in obj]
+    return obj
+
+
 def sh(args, timeout=10):
     try:
         return subprocess.run(args, capture_output=True, text=True, timeout=timeout)
@@ -510,23 +522,23 @@ def publish_state(mqc):
     client_dir = collect_client_dir()
     wan_rows = collect_wan()
 
-    mqc.publish(f"{state_root}/wan", json.dumps({"rows": wan_rows}))
+    mqc.publish(f"{state_root}/wan", json.dumps(mark_unavailable({"rows": wan_rows})))
     for ap, meta in zip(aps, APS):
-        mqc.publish(f"{state_root}/ap/{meta['id']}", json.dumps(ap))
+        mqc.publish(f"{state_root}/ap/{meta['id']}", json.dumps(mark_unavailable(ap)))
     mqc.publish(f"{state_root}/clients", json.dumps({"rows": collect_clients(aps, client_dir)}))
-    mqc.publish(f"{state_root}/starlink", json.dumps(collect_starlink()))
+    mqc.publish(f"{state_root}/starlink", json.dumps(mark_unavailable(collect_starlink())))
     mqc.publish(f"{state_root}/deploywarn", json.dumps(collect_deploywarn()))
     mqc.publish(f"{state_root}/wan_prefer", json.dumps({"prefer": read_prefer() or "auto"}))
 
     failover = read_json_file(FAILOVER_STATE)
     if failover is not None:
-        mqc.publish(f"{state_root}/failover", json.dumps(failover))
+        mqc.publish(f"{state_root}/failover", json.dumps(mark_unavailable(failover)))
     thermal = read_json_file(THERMAL_STATE)
     if thermal is not None:
-        mqc.publish(f"{state_root}/thermal", json.dumps(thermal))
+        mqc.publish(f"{state_root}/thermal", json.dumps(mark_unavailable(thermal)))
     battery = read_json_file(BATTERY_STATE)
     if battery is not None:
-        mqc.publish(f"{state_root}/battery", json.dumps(battery))
+        mqc.publish(f"{state_root}/battery", json.dumps(mark_unavailable(battery)))
 
     return wan_rows