refactor(webui): centralize native runtime access (#4769)

webui/src/App.tsx

@@ -57,7 +57,6 @@ import {
 } from "@/lib/api";
 import {
   createRuntimeHost,
-  getHostApi,
   toRuntimeSurface,
 } from "@/lib/runtime";
 import { projectNameFromPath } from "@/lib/workspace";
@@ -939,8 +938,8 @@ export default function App() {
   };
 
   const handleNativeEngineRestart = async (): Promise<string> => {
-    const hostApi = getHostApi();
-    if (!hostApi?.restartEngine) {
+    const runtimeHost = createRuntimeHost(state.runtimeSurface);
+    if (!runtimeHost.restartEngine) {
       throw new Error("native engine restart is unavailable");
     }
     rememberRestartRoute();
@@ -950,7 +949,7 @@ export default function App() {
       // ignore storage errors
     }
     try {
-      await hostApi.restartEngine();
+      await runtimeHost.restartEngine();
       const refreshed = await refreshReadyClient(state.client, state.runtimeSurface);
       return refreshed.token;
     } finally {