agent: Generate a notification when reaching tool use limit (#31894)

When reaching the consecutive tool call limit, the agent gets blocked
and without a notification, you wouldn't know that. This PR adds the
ability to be notified when that happens, and you can use either sound
_and_ toast, or just one of them.

Release Notes:

- agent: Added support for getting notified (via toast and/or sound)
when reaching the consecutive tool call limit.

crates/agent/src/thread.rs

@@ -1673,6 +1673,7 @@ impl Thread {
                                         }
                                         CompletionRequestStatus::ToolUseLimitReached => {
                                             thread.tool_use_limit_reached = true;
+                                            cx.emit(ThreadEvent::ToolUseLimitReached);
                                         }
                                     }
                                 }
@@ -2843,6 +2844,7 @@ pub enum ThreadEvent {
     },
     CheckpointChanged,
     ToolConfirmationNeeded,
+    ToolUseLimitReached,
     CancelEditing,
     CompletionCanceled,
 }