Warn user when configuring sketchbook under under IDE installation

[per1234]

Describe the request

If the user sets the "Sketchbook location" to a path under the Arduino IDE application installation folder, display a warning that clearly communicates that files stored in that path will be lost when the IDE is updated to a new version.

🙂 Loss of user files will be prevented.

Describe the current behavior

Arduino IDE 1.x has a "portable mode" feature, where the board packages and sketchbook may be stored inside the application installation folder.

Arduino IDE 2.x does not have any support for a portable mode feature (#122). However, users might attempt to use it in the same manner without realizing this fact.

Because the user's files will not be preserved through an update/uninstall, the Arduino IDE 1.x installer displays a warning that any files the user has stored inside the existing installation folder will be lost:

Since there is no reason to expect that there would be user files in the application folder, Arduino IDE 2.x does not do this.

🙁 If the user has attempted to use Arduino IDE in a "portable mode" configuration by setting the sketchbook folder to a path under the IDE installation, their files will be lost when they update the IDE. At best, it will be inconvenient to restore the sketchbook content. At worst, it will result in loss of irreplaceable data.

Arduino IDE version

2.3.7

Operating system

• Linux
• Windows

Operating system version

• Ubuntu 24.04
• Windows 11

Additional context

Originally requested at https://forum.arduino.cc/t/auto-update-deleted-my-portable-sketchbook/1420525

Issue checklist

• I searched for previous requests in the issue tracker
• I verified the feature was still missing when using the latest nightly build
• My request contains all necessary details