fix: include sdpi-bridge.js in packaged app via extraResources

The electron-builder 'files' array only packaged dist/, electron/, and
package.json. public/bridge/sdpi-bridge.js was never copied into the
app bundle.

In the packaged app (app.isPackaged === true), main.cjs looks for the
bridge at process.resourcesPath/bridge/sdpi-bridge.js. Since the file
was absent, net.fetch() returned ERR_FILE_NOT_FOUND, sdpi-bridge.js
failed to load, and window.sdpi was undefined in the inspector iframe —
causing 'ReferenceError: sdpi is not defined' when clicking Save.

Fix: add extraResources entry so electron-builder copies the bridge into
resources/bridge/sdpi-bridge.js during packaging.

Author: tech-stack-studios

package.json

@@ -36,6 +36,12 @@
       "electron/**",
       "package.json"
     ],
+    "extraResources": [
+      {
+        "from": "public/bridge/sdpi-bridge.js",
+        "to": "bridge/sdpi-bridge.js"
+      }
+    ],
     "linux": {
       "target": [
         {