fix: replace std::thread::sleep with tokio::time::sleep in async context (#831)

The `execute` method of `ShellWaitTool` is async, but used
`std::thread::sleep` which blocks the tokio worker thread. Replace with
`tokio::time::sleep().await` so other tasks can make progress during the
50ms poll interval.

crates/tui/src/tools/shell.rs

@@ -2438,7 +2438,7 @@ impl ToolSpec for ShellInteractTool {
                 return Ok(build_shell_delta_tool_result(delta));
             }
 
-            std::thread::sleep(Duration::from_millis(50));
+            tokio::time::sleep(Duration::from_millis(50)).await;
             elapsed = elapsed.saturating_add(50);
         }
     }