fix: open external links in VS Code runtime

Route shared URL opening through VS Code host instead of webview window APIs
Add a VS Code runtime URL-open API and bridge handler using vscode.env.openExternal
Keep shared URL helper behavior unchanged for desktop and web

packages/ui/src/lib/api/types.ts

@@ -619,6 +619,7 @@ export interface EditorAPI {
 export interface VSCodeAPI {
   executeCommand(command: string, ...args: unknown[]): Promise<unknown>;
   openAgentManager(): Promise<void>;
+  openExternalUrl(url: string): Promise<void>;
 }
 
 export interface PushSubscribePayload {

packages/ui/src/lib/url.ts

@@ -1,3 +1,5 @@
+import { getRegisteredRuntimeAPIs } from '@/contexts/runtimeAPIRegistry';
+
 /**
  * Utility for opening external URLs with Tauri shell support.
  * In desktop runtime, uses tauri.shell.open() for proper system browser handling.
@@ -55,6 +57,16 @@ export const openExternalUrl = async (url: string): Promise<boolean> => {
 
   const normalizedTarget = parsed.toString();
 
+  const runtimeApis = getRegisteredRuntimeAPIs();
+  if (runtimeApis?.runtime?.isVSCode && runtimeApis.vscode?.openExternalUrl) {
+    try {
+      await runtimeApis.vscode.openExternalUrl(normalizedTarget);
+      return true;
+    } catch {
+      return false;
+    }
+  }
+
   const tauri = (window as unknown as { __TAURI__?: TauriShell }).__TAURI__;
   if (tauri?.shell?.open) {
     try {