Use full Trailhead Path Bookmarker name everywhere

- Popup header: tray icon + "Trailhead Path Bookmarker" title
- HTML <title>, electron-builder productName, and tray tooltip all match
- Popup width budget now also factors in the header's intrinsic width
  (icon + title + actions), so the brand never gets ellipsized — measured
  via h1 scrollWidth so overflow:hidden doesn't lie about content size

package.json

@@ -29,7 +29,7 @@
   },
   "build": {
     "appId": "com.dbeuttel.folder-bookmark-tray",
-    "productName": "Trailhead",
+    "productName": "Trailhead Path Bookmarker",
     "files": [
       "electron/**/*",
       "dist/**/*",