feat: detect missing lldpd and add install_lldpd action

get_device_warnings() now reports lldpd_not_installed (action
install_lldpd) when lldpd is absent, matching the existing
OpenWrt pattern. run_device_action("install_lldpd") installs and
enables lldpd via apt/systemd so LLDP topology links to directly
connected switches can be discovered.

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

napalm_proxmox/driver.py

@@ -1763,11 +1763,24 @@ class ProxmoxDriver(HypervisorDriver):
         """Return warnings for the Proxmox node.
 
         Currently detects:
+        - lldpd not installed (LLDP neighbor discovery unavailable)
         - Available package updates (via Proxmox APT API)
         - Missing / invalid subscription
         """
         warnings: list[_JsonDict] = []
 
+        # 0. LLDP daemon
+        try:
+            lldpd_path = self._exec_ssh_command("command -v lldpd 2>/dev/null").strip()
+            if not lldpd_path:
+                warnings.append({
+                    "code": "lldpd_not_installed",
+                    "severity": "warning",
+                    "action": "install_lldpd",
+                })
+        except Exception:
+            pass
+
         # 1. Available package updates
         try:
             updates = self._api.nodes(self._node_name).apt.update.get()
@@ -2217,8 +2230,39 @@ class ProxmoxDriver(HypervisorDriver):
         """Execute a named administrative action on the Proxmox node."""
         if action == "fix_snmp":
             return self._action_fix_snmp()
+        if action == "install_lldpd":
+            return self._action_install_lldpd()
         raise NotImplementedError(f"Unknown action: {action!r}")
 
+    def _action_install_lldpd(self) -> dict:
+        """Install, enable and start lldpd on the Proxmox node.
+
+        Proxmox runs Debian/Linux underneath, so this is a plain apt install
+        followed by enabling the systemd service. lldpd's defaults (listen on
+        all interfaces) are sufficient to discover the directly-connected
+        switch via the management bridge (e.g. vmbr0).
+        """
+        lines: list[str] = []
+
+        install_out = self._exec_ssh_command(
+            "DEBIAN_FRONTEND=noninteractive apt-get install -y lldpd 2>&1 | tail -5"
+        )
+        lines.append(f"[install] {install_out.strip()[-200:]}")
+
+        enable_out = self._exec_ssh_command(
+            "systemctl enable --now lldpd 2>&1 || service lldpd start 2>&1 || true"
+        )
+        lines.append(f"[service] {enable_out.strip()[-200:]}")
+
+        verify = self._exec_ssh_command("command -v lldpd 2>/dev/null").strip()
+        success = bool(verify)
+        if success:
+            lines.append("[ok] lldpd installed. Neighbors will appear after a short warm-up period.")
+        else:
+            lines.append("[warn] lldpd does not appear to be installed after the attempt.")
+
+        return {"success": success, "output": "\n".join(lines)}
+
     def _action_fix_snmp(self) -> dict:
         """Install, configure and start snmpd on the Proxmox node.