Snap strict confinement: GitUI misreports repository NotFound as “non-bare repository”

[Yi2255]

Describe the bug
Using the snap version of gitui in strict confinement mode, running gitui in a valid non-bare repository outside snap-allowed paths (for example /i4) shows a misleading error:

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

The repository is actually non-bare. The real issue is repository discovery failure (NotFound), not a bare-repository problem.

To Reproduce
Steps to reproduce the behavior:

1. Install gitui from snap:
   snap install gitui
2. Create a repository outside /home (for example /i4/repo):
   mkdir -p /i4/repo
   cd /i4/repo
   git init
3. Verify the repository is non-bare:
   git rev-parse --is-bare-repository
   (output should be false)
4. Run gitui and see error.

Expected behavior
gitui should report the actual cause (repository open/discovery failure due to snap strict path confinement), instead of incorrectly telling users to run inside a non-bare repository.

Screenshots
N/A. Terminal output is included above.

Context (please complete the following information):

• OS/Distro + Version: Ubuntu 24.04.3 LTS
• GitUI Version [e.g. 0.5]: snap package (strict confinement)
• Rust version: N/A (prebuilt snap binary)

Additional context