fix: call ripgrep with explicit utf-8 encoding.

[Sola-ris]

Summary

Call ripgrep with explicit UTF-8 encoding to prevent issues with multi-byte characters.

When calling subprocess.Popen, (which is where silent_subprocess::silent_run eventually ends up) with text=True without specifying the encoding, python will use the encoding returned by locale::getencoding.

On Linux this returns UTF-8 while on Windows it will return cp1252 which causes issues with multi-byte characters like em dashes or Japanese characters.

Fixes #1195.

Before

I've omitted こんにちは.txt from the screenshot since it hangs the program with the error reported in #1195

After

Tasks Completed

• Platforms Tested:
  • Windows x86
  • Windows ARM
  • macOS x86
  • macOS ARM
  • Linux x86
  • Linux ARM
• Tested For:
  • Basic functionality
  • PyInstaller executable

[Computerdores]

Code looks good, also very nice that you wrote a regression test