fix(electron): point main + preload + index paths at the real build layout

npm run dev failed with ERR_MODULE_NOT_FOUND for dist-electron/services/inputHelper.

Root cause: the electron program includes src runtime files (repositories,
layoutProfile, ocrPreprocess), so tsc's inferred rootDir is the project root and
it emits the entry at dist-electron/electron/main.js (with src at
dist-electron/src). package.json "main" still pointed at a stale flat
dist-electron/main.js fossil from an older build layout, whose extensionless
imports don't resolve under NodeNext ESM.

- package.json main -> dist-electron/electron/main.js.
- predev/build copy preload.cjs into dist-electron/electron/ (next to main.js,
  where main.ts resolves it via __dirname).
- main.ts loads ../../dist/index.html (one level deeper now) for the packaged
  window + overlay.

Verified: clean electron build emits only the nested layout; electron . loads the
main process past module resolution (only ERR_CONNECTION_REFUSED for the dev
server, expected standalone); npm run build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

electron/main.ts

@@ -394,7 +394,7 @@ function createMainWindow() {
   if (isDev) {
     mainWindow.loadURL(process.env.VITE_DEV_SERVER_URL!);
   } else {
-    mainWindow.loadFile(path.join(__dirname, "../dist/index.html"));
+    mainWindow.loadFile(path.join(__dirname, "../../dist/index.html"));
   }
 }
 
@@ -528,7 +528,7 @@ function createOverlayWindow() {
   if (isDev) {
     overlayWindow.loadURL(`${process.env.VITE_DEV_SERVER_URL!}?overlay=1`);
   } else {
-    overlayWindow.loadFile(path.join(__dirname, "../dist/index.html"), {
+    overlayWindow.loadFile(path.join(__dirname, "../../dist/index.html"), {
       query: { overlay: "1" },
     });
   }