Improve fuzzy search for the @ filename select

[remorses]

Right now @ can't find files if I don't specify the prefix of the file exactly, use fuzzy search instead

[saraford]

Thank you for the feedback! It doesn't look like anyone has submitted this suggestion yet. Can you add your suggestion here so you can follow its progress and discussion: https://github.com/google-gemini/gemini-cli/issues/new?template=feature_request.yml

[remorses]

Opened an issue here: #1870