Disable active probes — passive-only operation required

arping/ICMP probes on device appearance violate the passive-only
design constraint. Stub out _fire_active_probes to return immediately.

net_alerter/net_alerter.py

@@ -170,15 +170,13 @@ def _create_identity_record(identity_id: str) -> dict:
 
 
 def _fire_active_probes(identity_id: str, mac: str, signal_type: str, dhcp_fp: str) -> None:
-    """Fire active probes when a new device identity is created.
+    """Disabled — passive-only operation. No active probes sent."""
+    return
 
-    Non-blocking: runs probes in a thread to avoid stalling the main loop.
-    Attempts ARP ping if IP available, or mDNS query if hostname available.
-    """
+
+def _fire_active_probes_DISABLED(identity_id: str, mac: str, signal_type: str, dhcp_fp: str) -> None:
     def _probe_worker():
         try:
-            # For now, log that probes were fired. Real probe logic can use scapy or zeroconf if available.
-            # This is a non-blocking thread so we don't stall the correlator.
             with device_store_lock:
                 if identity_id not in device_store:
                     return