feat: add wait tool implementation for collab (#9088)

Add implementation for the `wait` tool.

For this we consider all status different from `PendingInit` and
`Running` as terminal. The `wait` tool call will return either after a
given timeout or when the tool reaches a non-terminal status.

A few points to note:
* The usage of a channel is preferred to prevent some races (just
looping on `get_status()` could "miss" a terminal status)
* The order of operations is very important, we need to first subscribe
and then check the last known status to prevent race conditions
* If the channel gets dropped, we return an error on purpose

codex-rs/protocol/src/protocol.rs

@@ -699,7 +699,7 @@ pub enum AgentStatus {
     Completed(Option<String>),
     /// Agent encountered an error.
     Errored(String),
-    /// Agent has been shutdowned.
+    /// Agent has been shutdown.
     Shutdown,
     /// Agent is not found.
     NotFound,