docs(electron-vite): explain why zod is bundled into preload (P2-17)

electron.vite.config.ts

@@ -29,6 +29,9 @@ export default defineConfig({
     },
   },
   preload: {
+    // zod is bundled into preload because preload runs as sandboxed CJS
+    // and cannot resolve externalized ESM deps at runtime. Inlining keeps
+    // IPC Zod validation working inside the preload layer.
     plugins: [externalizeDepsPlugin({ exclude: ["zod"] })],
     resolve: {
       alias: {