Network Reconnection Delay

Nucleic-Session: 4BE3E40C-E939-444C-8AED-93C0AFE13C07
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Models/HostConnection.swift

@@ -689,6 +689,33 @@ final class HostConnection {
         }
     }
 
+    /// Foreground liveness check — the fast-reconnect path. iOS suspends the app when it's
+    /// backgrounded, which silently kills the socket; but no `.closed`/`.failed` reaches us while
+    /// we're frozen, so this connection can wake still marked `.connected`. Trusting that stale
+    /// state means nothing reconnects until the 55s keepalive deadline (or ~15s TCP keepalive)
+    /// finally notices — the several-second (or worse) stall on return. Instead: if we're already
+    /// not live, re-dial now with no backoff; if we *look* live, actively ping and re-dial the
+    /// instant the link fails to answer within a tight deadline. A pinned host only (a host
+    /// mid-pairing runs its own one-shot chain and has no `pinnedHost`).
+    func revalidate() {
+        guard let host = pinnedHost else { return }
+        guard connectivity.isLive, let client else {
+            reconnectAttempts = 0
+            reconnect(to: host)
+            return
+        }
+        revalidateTask?.cancel()
+        revalidateTask = Task { [weak self] in
+            let alive = await client.probeAlive(within: .milliseconds(800))
+            guard !Task.isCancelled, let self, self.client === client,
+                  self.connectivity.isLive else { return }
+            if !alive {
+                self.reconnectAttempts = 0
+                self.reconnect(to: host)
+            }
+        }
+    }
+
     private func scheduleRetry(host: PairedHost?) {
         guard let host else { return }
         reconnectAttempts += 1