fix: restore connectivity alerts for overdue/unknown/down hosts on startup

restore_connection_timers now calls _set_connectivity_alert("CRITICAL")
for DOWN, OVERDUE, and UNKNOWN connections, ensuring alerts are present
even if hbd was shut down before the transition callbacks recorded them.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hbd/server/udp.py

@@ -266,10 +266,15 @@ def restore_connection_timers(hbdclass, ctx):
         for afam, conn in list(host.connections.items()):
             state = conn.getstate()
             if state == hbdclass.Connection.DOWN:
+                _set_connectivity_alert(host, afam, "CRITICAL")
                 continue
 
             on_overdue, on_unknown = _make_timer_callbacks(uname, host, ctx)
 
+            if state == hbdclass.Connection.UNKNOWN:
+                _set_connectivity_alert(host, afam, "CRITICAL")
+                continue
+
             if state == hbdclass.Connection.UP and interval > 0:
                 elapsed = now - conn.lastbeat
                 # Give hosts one full (interval + grace) of extra time on startup
@@ -300,6 +305,10 @@ def restore_connection_timers(hbdclass, ctx):
                         "Restored OVERDUE timer %s/%s: %.0fs remaining",
                         uname, afam, remaining,
                     )
+                # Ensure the connectivity alert is set — it may be missing if
+                # hbd was shut down before the on_overdue callback had a chance
+                # to record it.
+                _set_connectivity_alert(host, afam, "CRITICAL")
                 restored += 1
 
     logger.info("Restored timers for %d connection(s)", restored)
@@ -470,6 +479,7 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
     boot = msg.get("boot", 0)
 
     if boot:
+        # hbc was stared with a -b flag
         eventlog(uname, "INFO", "booted")
         if host.watched:
             asyncio.create_task(notify_mod.send_notification(
@@ -480,6 +490,7 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
         eventlog(uname, "INFO", message, service=service)
 
     if conn.getstate() != hbdcls.Connection.UP:
+        # Transition to UP and log/notify if appropriate
         lasts = conn.state
         d = conn.newstate(hbdcls.Connection.UP, now)
         # On reboot, pre-boot plugin data and derived alerts are stale.