refactor: replace VS Code toast with chat message

- Remove short-lived toast when opening VS Code
- Add persistent message in chat instead
- Remove artificial delay when opening VS Code
- Keep error handling with toasts for failed cases

frontend/src/components/file-explorer/FileExplorer.tsx

@@ -12,6 +12,7 @@ import { useTranslation } from "react-i18next";
 import { twMerge } from "tailwind-merge";
 import AgentState from "#/types/AgentState";
 import { setRefreshID } from "#/state/codeSlice";
+import { addAssistantMessage } from "#/state/chatSlice";
 import IconButton from "../IconButton";
 import ExplorerTree from "./ExplorerTree";
 import toast from "#/utils/toast";
@@ -174,14 +175,8 @@ function FileExplorer({ error, isOpen, onToggle }: FileExplorerProps) {
     try {
       const response = await OpenHands.getVSCodeUrl();
       if (response.vscode_url) {
-        toast.success(
-          `open-vscode-${new Date().getTime()}`,
-          t(I18nKey.EXPLORER$VSCODE_SWITCHING_MESSAGE),
-        );
-        setTimeout(
-          () => window.open(response.vscode_url ?? "", "_blank"),
-          3000,
-        );
+        dispatch(addAssistantMessage("You opened VS Code. Please inform the agent of any changes you made to the workspace or environment. To avoid conflicts, it's best to pause the agent before making any changes."));
+        window.open(response.vscode_url, "_blank");
       } else {
         toast.error(
           `open-vscode-error-${new Date().getTime()}`,