BUG: Error invalid path on valid git repo using `reftable` backend.

[groutoutlook]

Describe the bug gitui emit errors on some random(?) repo.

To Reproduce Steps to reproduce the behavior:

1. Clone anything with Git 2.45+
2. Try to invoke gitui on it.
3. See error

$ gitui
invalid path
please run gitui inside of a non-bare git repository

Expected behavior It should read the path as normal and pop out a TUI.

Screenshots

Context (please complete the following information):

• OS/Distro + Version: Windows 11 Pro x86_64 Build 10.0.26200.5761 (25H2)
• GitUI Version: gitui 0.27.0 2025-01-14 (99f6967)
• Rust version: Prebuilt on Releases.

Additional context

1. lazygit can consume that path just fine.
2. After trying to clone gitui to build locally with rustc version 1.89.0 (29483883e 2025-08-04), I got

Error: unsupported extension name extensions.refstorage; class=Repository (6)

3. Maybe it's libgit2 error? please look more into it.

• Due to dependent on git2, gitui cant resolve reftable backend, and that's fine for me.