Handle authorization send errors instead of silently dropping with .ok() (#48639)

The two `unbounded_send` calls in `ToolCallEventStream`'s authorize
methods were using `.ok()` to silently discard send failures. This meant
that if the authorization channel was closed, the tool call would hang
indefinitely waiting for a response that would never come.

## Changes

- Both `authorize_third_party_tool` and `authorize` methods now use `if
let Err(error)` to detect send failures
- On failure, logs the error with `log::error!` and returns
`Task::ready(Err(...))` so callers get immediate, meaningful feedback

Release Notes:

- Tool authorization failures are now logged and reported instead of
being silently ignored.

crates/agent/src/thread.rs

@@ -3128,7 +3128,8 @@ impl ToolCallEventStream {
         }
 
         let (response_tx, response_rx) = oneshot::channel();
-        self.stream
+        if let Err(error) = self
+            .stream
             .0
             .unbounded_send(Ok(ThreadEvent::ToolCallAuthorization(
                 ToolCallAuthorization {
@@ -3172,7 +3173,12 @@ impl ToolCallEventStream {
                     context: None,
                 },
             )))
-            .ok();
+        {
+            log::error!("Failed to send tool call authorization: {error}");
+            return Task::ready(Err(anyhow!(
+                "Failed to send tool call authorization: {error}"
+            )));
+        }
 
         let fs = self.fs.clone();
         cx.spawn(async move |cx| {
@@ -3224,7 +3230,8 @@ impl ToolCallEventStream {
         let options = context.build_permission_options();
 
         let (response_tx, response_rx) = oneshot::channel();
-        self.stream
+        if let Err(error) = self
+            .stream
             .0
             .unbounded_send(Ok(ThreadEvent::ToolCallAuthorization(
                 ToolCallAuthorization {
@@ -3237,7 +3244,12 @@ impl ToolCallEventStream {
                     context: Some(context),
                 },
             )))
-            .ok();
+        {
+            log::error!("Failed to send tool call authorization: {error}");
+            return Task::ready(Err(anyhow!(
+                "Failed to send tool call authorization: {error}"
+            )));
+        }
 
         let fs = self.fs.clone();
         cx.spawn(async move |cx| {