Put cells in pending mode immediately when the user clicks run. Remove them from the pending state if the controller does not create an execution immediately inside the execute handler.

src/vs/workbench/api/common/extHostNotebookKernels.ts

@@ -341,7 +341,7 @@ export class ExtHostNotebookKernels implements ExtHostNotebookKernelsShape {
 		if (cell) {
 			this._onDidChangeCellExecutionState.fire({
 				cell: cell.apiCell,
-				state: state ?? ExtHostNotebookCellExecutionState.Idle
+				state: state ? extHostTypeConverters.NotebookCellExecutionState.to(state) : ExtHostNotebookCellExecutionState.Idle
 			});
 		}
 	}