fix: never park the last present family as absent

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uc9V1v7iXruubpoLiSE24M

hbd/server/udp.py

@@ -249,7 +249,11 @@ def _make_timer_callbacks(uname, host, ctx):
             return
         now = time.time()
         afam = connection.afam
-        if not host.flag_present(afam):
+        # Park only while some other family is still present: the last monitored family
+        # must never be parked silently, or a host whose client reports no internet on any
+        # protocol would die without an alert.
+        if not host.flag_present(afam) and any(
+                af != afam and host.family_present(af) for af in host.connections):
             # The client says this protocol has no connectivity: not an outage.
             connection.newstate(cls.ABSENT, now)
             connection.cancel_overdue_timer()
@@ -258,6 +262,8 @@ def _make_timer_callbacks(uname, host, ctx):
                 msg_to_websockets("host", host.stateinfo())
             return
 
+        # If any connection is DOWN (clean shutdown reported) Host.status() is "down", so a
+        # later overdue of the other family raises no separate event/alert; the shutdown did.
         prev = host.status()
         connection.newstate(cls.OVERDUE, now, cfg.get("grace", 2))
         new = host.status()