Handle ROUTING_APP error response in onResponseTraceRoute

Previously, receiving a ROUTING_APP packet in response to a traceroute
would cause the function to attempt parsing it as a RouteDiscovery
payload, resulting in a crash or silent failure followed by a timeout.

This mirrors the error handling already present in onResponseTelemetry
and onResponseWaypoint, but displays the specific errorReason instead
of a hardcoded firmware version message, since traceroute is a
diagnostic tool where the exact failure reason is more valuable.

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

meshtastic/mesh_interface.py

@@ -687,6 +687,12 @@ class MeshInterface:  # pylint: disable=R0902
 
     def onResponseTraceRoute(self, p: dict):
         """on response for trace route"""
+        if p["decoded"]["portnum"] == "ROUTING_APP":
+            error = p["decoded"]["routing"]["errorReason"]
+            print(f"Traceroute failed: {error}")
+            self._acknowledgment.receivedTraceRoute = True
+            return
+
         UNK_SNR = -128 # Value representing unknown SNR
 
         routeDiscovery = mesh_pb2.RouteDiscovery()