feat: bootstrap secure cross-platform assistant

Establish the Electron foundation and pluggable agent runtime so desktop workflows can evolve safely across supported platforms.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

vitest.config.ts

@@ -0,0 +1,13 @@
+import react from '@vitejs/plugin-react'
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'jsdom',
+    setupFiles: ['./src/renderer/src/test-setup.ts'],
+    coverage: {
+      reporter: ['text', 'html']
+    }
+  }
+})