agent: add nordlynx VPN status to metrics

Detects nordlynx WireGuard interface on hosts that run NordVPN and
includes active/inactive status in the metrics payload. JARVIS alerts.php
will generate a critical alert and auto-restart nordvpnd if it goes down.

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

agent/jarvis-agent.py

@@ -265,11 +265,23 @@ def get_load() -> list:
     except Exception:
         return [0, 0, 0]
 
+def get_nordvpn_status() -> dict | None:
+    """Check nordlynx WireGuard interface. Returns None if nordlynx not present on this host."""
+    try:
+        r = subprocess.run(["ip", "link", "show", "nordlynx"],
+                           capture_output=True, text=True, timeout=3)
+        if r.returncode != 0:
+            return None
+        active = "UP,LOWER_UP" in r.stdout or "state UP" in r.stdout
+        return {"active": active, "interface": "nordlynx"}
+    except Exception:
+        return None
+
 def collect_metrics(cfg: dict) -> dict:
     # First reading for CPU delta
     get_cpu_percent()
     time.sleep(1)
-    return {
+    metrics = {
         "hostname":    cfg.get("hostname", socket.gethostname()),
         "cpu_percent": get_cpu_percent(),
         "memory":      get_memory(),
@@ -280,6 +292,10 @@ def collect_metrics(cfg: dict) -> dict:
         "platform":    platform.system(),
         "timestamp":   datetime.utcnow().isoformat() + "Z",
     }
+    nordvpn = get_nordvpn_status()
+    if nordvpn is not None:
+        metrics["nordvpn"] = nordvpn
+    return metrics
 
 # ── Proxmox metrics ───────────────────────────────────────────────────────────