refactor: mark public enums as non-exhaustive to improve API stability

Apply the #[non-exhaustive] attribute to ClientError and WarningKind to prevent breaking changes when adding new variants. Handle the catch-all case in the CLI formatter.

crates/irtt-cli/src/lib.rs

@@ -831,6 +831,7 @@ fn warning_kind(kind: WarningKind) -> &'static str {
         WarningKind::MalformedOrUnrelatedPacket => "malformed_or_unrelated_packet",
         WarningKind::WrongToken => "wrong_token",
         WarningKind::UntrackedReply => "untracked_reply",
+        _ => "unknown",
     }
 }
 

crates/irtt-client/src/error.rs

@@ -3,6 +3,7 @@ use std::{io, time::Duration};
 use thiserror::Error;
 
 #[derive(Debug, Error)]
+#[non_exhaustive]
 pub enum ClientError {
     #[error("failed to resolve server address {addr:?}")]
     Resolve { addr: String },

crates/irtt-client/src/event.rs

@@ -101,6 +101,7 @@ pub enum ClientEvent {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum WarningKind {
     MalformedOrUnrelatedPacket,
     WrongToken,