feat(client): Reject empty open_timeouts configuration with dedicated error

crates/irtt-client/src/client.rs

@@ -791,4 +791,16 @@ mod tests {
             Err(ClientError::OpenTimeoutTooSmall { .. })
         ));
     }
+
+    #[test]
+    fn empty_open_timeouts_is_rejected() {
+        let config = ClientConfig {
+            open_timeouts: vec![],
+            ..ClientConfig::default()
+        };
+        assert!(matches!(
+            Client::connect(config),
+            Err(ClientError::NoOpenTimeouts)
+        ));
+    }
 }

crates/irtt-client/src/error.rs

@@ -17,6 +17,8 @@ pub enum ClientError {
         timeout: Duration,
         minimum: Duration,
     },
+    #[error("open_timeouts must not be empty")]
+    NoOpenTimeouts,
     #[error("server rejected the open request")]
     ServerRejected,
     #[error("unexpected no-test open reply")]

crates/irtt-client/src/socket.rs

@@ -11,6 +11,9 @@ use crate::{
 };
 
 pub(crate) fn validate_open_timeouts(timeouts: &[Duration]) -> Result<(), ClientError> {
+    if timeouts.is_empty() {
+        return Err(ClientError::NoOpenTimeouts);
+    }
     for timeout in timeouts {
         if *timeout < MIN_OPEN_TIMEOUT {
             return Err(ClientError::OpenTimeoutTooSmall {