fix: send boot/shutdown on first open connection, not blindly first in list

Replace break-after-first-iteration with next(c for c in connections if
c.transport) so the message goes to the first connection that actually
has an open transport. Falls back to connections[0] if none are open
yet (sendto will attempt reopen), avoiding silent message loss when the
leading connection is still connecting.

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

scripts/hbc_mini.py

@@ -1052,9 +1052,8 @@ async def _async_main(args, cfg: Dict[str, Any]) -> int:
         if args.message:
             bmsg["service"] = "service"
             bmsg["msg"] = args.message
-        for c in connections:
-            await c.sendto(bmsg)
-            break
+        target = next((c for c in connections if c._transport), connections[0])
+        await target.sendto(bmsg)
         if args.message and not args.daemon:
             await asyncio.sleep(0.3)
             for c in connections:
@@ -1086,12 +1085,12 @@ async def _async_main(args, cfg: Dict[str, Any]) -> int:
         pass
 
     log.info("shutting down")
-    for conn in connections:
+    target = next((c for c in connections if c._transport), connections[0] if connections else None)
+    if target:
         try:
-            await conn.sendto({"shutdown": 1, "acks": conn.ackcount})
+            await target.sendto({"shutdown": 1, "acks": target.ackcount})
         except Exception:
             pass
-        break
     for conn in connections:
         conn.close()
     await asyncio.sleep(0.3)