feat: include remote chassis MAC in LLDP neighbor entries

Enables MAC-based topology matching against devices that report their
own MAC but not a usable system name.

napalm_linux/linux.py

@@ -257,10 +257,15 @@ class LinuxDriver(OSDriver):
             entries.setdefault(iface, {})[subkey] = value
 
         for iface, data in entries.items():
-            neighbors.setdefault(iface, []).append({
+            entry = {
                 "hostname": data.get("chassis.name", ""),
                 "port": data.get("port.ifname", data.get("port.id.value", "")),
-            })
+            }
+            if data.get("chassis.id.subtype") == "mac":
+                mac = data.get("chassis.id.value", "")
+                if re.match(r"^([0-9A-Fa-f]{2}:){5}[0-9A-Fa-f]{2}$", mac):
+                    entry["mac"] = mac.lower()
+            neighbors.setdefault(iface, []).append(entry)
 
         return neighbors