fix(home-assistant): disable otbr-agent, ZBT-2 antenna not connected

otbr-agent can't reach the Thread radio without the antenna attached
and crash-loops on every switch, failing the rebuild.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QD5x9KR8cM7EPPsxKATHfQ

modules/environments/home-assistant/default.nix

@@ -54,14 +54,16 @@ in
       "f /var/lib/hass/scenes.yaml 0644 hass hass - []"
     ];
 
-    services.openthread-border-router = {
-      enable = true;
-      package = pkgs.unstable.openthread-border-router;
-      openFirewall = true;
-      backboneInterfaces = [ "enp3s0" ];
-      radio.device = "/dev/serial/by-id/usb-Nabu_Casa_ZBT-2_DCB4D9149C7C-if00";
-      radio.baudRate = 460800;
-    };
+    # Disabled: ZBT-2 antenna isn't connected, so otbr-agent can't reach the
+    # radio and just crash-loops on every switch.
+    # services.openthread-border-router = {
+    #   enable = true;
+    #   package = pkgs.unstable.openthread-border-router;
+    #   openFirewall = true;
+    #   backboneInterfaces = [ "enp3s0" ];
+    #   radio.device = "/dev/serial/by-id/usb-Nabu_Casa_ZBT-2_DCB4D9149C7C-if00";
+    #   radio.baudRate = 460800;
+    # };
 
     my.homepage.services = [
       {