feat: make interrupt state not final for multi-agents (#13850)

Make `interrupted` an agent state and make it not final. As a result, a
`wait` won't return on an interrupted agent and no notification will be
send to the parent agent.

The rationals are:
* If a user interrupt a sub-agent for any reason, you don't want the
parent agent to instantaneously ask the sub-agent to restart
* If a parent agent interrupt a sub-agent, no need to add a noisy
notification in the parent agen

codex-rs/protocol/src/protocol.rs

@@ -1518,6 +1518,8 @@ pub enum AgentStatus {
     PendingInit,
     /// Agent is currently running.
     Running,
+    /// Agent's current turn was interrupted and it may receive more input.
+    Interrupted,
     /// Agent is done. Contains the final assistant message.
     Completed(Option<String>),
     /// Agent encountered an error.