fix(server): restore keeps connectivity alert for connections dropped to unknown

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

hbd/server/udp.py

@@ -351,6 +351,7 @@ def restore_connection_timers(hbdclass, ctx):
                 restored += 1
 
             elif state == hbdclass.Connection.OVERDUE:
+                host_overdue = host.status() == "overdue"
                 elapsed_overdue = now - conn.statetime
                 remaining = DROPOVERDUE - elapsed_overdue
                 if remaining <= 1:
@@ -360,6 +361,9 @@ def restore_connection_timers(hbdclass, ctx):
                         "Marking %s/%s UNKNOWN (overdue %.1f days)",
                         uname, afam, elapsed_overdue / 86400,
                     )
+                    # A connection dropped to UNKNOWN keeps its alert, like the
+                    # UNKNOWN branch above and on_unknown do.
+                    host_overdue = True
                 else:
                     conn.reset_overdue_timer(remaining, on_unknown)
                     logger.debug(
@@ -369,7 +373,7 @@ def restore_connection_timers(hbdclass, ctx):
                 # 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.
-                if host.status() == "overdue":
+                if host_overdue:
                     _set_connectivity_alert(host, afam, "CRITICAL")
                 restored += 1