fix(desktop): guard invoke calls with isTauriRuntime check

Step 5 (embedding config) and Step 5b (summary driver) in App.tsx
bootstrap called invoke() without checking if Tauri IPC is available.
When accessing http://localhost:1420/ in a regular browser, this caused
"Cannot read properties of undefined (reading 'transformCallback')".

Also added __TAURI_INTERNALS__ guard in saasStore kernel config sync.

desktop/src/App.tsx

@@ -261,7 +261,8 @@ function App() {
         // Non-critical, continue without heartbeat
       }
 
-      // Step 5: Restore embedding config to Rust backend
+      // Step 5: Restore embedding config to Rust backend (Tauri-only)
+      if (isTauriRuntime()) {
         try {
           // Migrate plaintext embedding apiKey to secure storage if present
           try {
@@ -319,6 +320,7 @@ function App() {
           log.warn('Failed to configure summary driver:', sumErr);
           // Non-critical, summaries won't be auto-generated
         }
+      }
 
       // Step 6: Bootstrap complete
       setBootstrapping(false);

desktop/src/store/saasStore.ts

@@ -542,7 +542,7 @@ export const useSaaSStore = create<SaaSStore>((set, get) => {
         const kernelConfigs = result.configs.filter(
           (c) => kernelCategories.includes(c.category) && c.value !== null
         );
-        if (kernelConfigs.length > 0) {
+        if (kernelConfigs.length > 0 && typeof window !== 'undefined' && '__TAURI_INTERNALS__' in window) {
           try {
             const { invoke } = await import('@tauri-apps/api/core');
             await invoke('kernel_apply_saas_config', {