Network Type Transition Optimization

Nucleic-Session: 40F8C53A-F001-423A-8607-EAE181DBE14B
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Models/HostConnection.swift

@@ -483,6 +483,27 @@ final class HostConnection {
         Task { await client.send(msg) }
     }
 
+    /// The device's network path changed (Wi-Fi ⇄ cellular, joined/left a network). React now rather
+    /// than waiting for a zombie LAN socket to time out or the reconnect backoff to elapse — this is
+    /// what makes the transport switch feel immediate. Only reconnect-managed hosts (a pinned host)
+    /// re-plan here; a host mid-pairing runs its own one-shot candidate chain.
+    func networkPathChanged() {
+        guard let host = pinnedHost else { return }
+        // Using (or dialing) LAN but LAN is no longer reachable → the socket is dead in all but name.
+        // Drop it and re-plan now; `buildCandidates` skips LAN and dials tailnet/relay.
+        if activeTransport == .lan, !pathMonitor.canUseLAN {
+            reconnectAttempts = 0
+            reconnect(to: host)
+            return
+        }
+        // Offline/reconnecting and the network just came back or changed → retry immediately instead
+        // of sitting out the remaining backoff.
+        if !connectivity.isLive, pathMonitor.isSatisfied {
+            reconnectAttempts = 0
+            reconnect(to: host)
+        }
+    }
+
     private func scheduleRetry(host: PairedHost?) {
         guard let host else { return }
         reconnectAttempts += 1