Fix crash when opening lazygit at the root of a bare repository

[pedrampdd]

Fixes #5469.

The bug

When the user runs lazygit from the root of a bare repository (a folder where .git points at a sibling .bare directory and worktrees live alongside it), lazygit crashes immediately with:

*errors.errorString Error getting repo paths: 'git -C <dir> rev-parse --path-format=absolute --show-toplevel --absolute-git-dir --git-common-dir --is-bare-repository --show-superproject-working-tree' failed: fatal: this operation must be run in a work tree

Reproduction (from the issue):

mkdir prom && cd prom
git clone --bare https://github.com/octocat/Hello-World.git .bare
echo 'gitdir: ./.bare' > .git
git worktree add foo HEAD
lazygit       # crashes here

Root cause

GetRepoPathsForDir calls git rev-parse --show-toplevel --absolute-git-dir --git-common-dir --is-bare-repository --show-superproject-working-tree. --show-toplevel exits non-zero with fatal: this operation must be run in a work tree when there is no working tree, so the entire query fails before the --is-bare-repository flag is ever inspected.

Lazygit already has explicit handling for bare repos (pkg/gui/recent_repos_panel.go checks git.Status.IsBareRepo() and surfaces a "Lazygit does not yet support bare repos. Open most recent repo?" prompt) but that path was unreachable because path discovery crashed first.

The fix

If the full rev-parse fails, retry without --show-toplevel. If the fallback reports is-bare-repository=true, build the RepoPaths value with the parent of the git dir as the worktree path (which is the directory the user invoked lazygit from). The non-bare fast path is unchanged: it's still a single rev-parse call.

If the fallback also fails, or if it succeeds but reports the repo is not bare, the original error is surfaced unchanged so genuine "not a git repository" failures still look the same to users.

Verification

• New tests bare repo without working tree (new fallback succeeds) and rev-parse fails with non-bare cause (fallback runs but original error is preserved) pass alongside the existing scenarios.
• All pkg/commands/... tests pass.
• Manual repro using the reproduction steps above: before the fix lazygit crashes; after the fix it shows the existing "does not yet support bare repos. Open most recent repo?" prompt — strictly better than a crash, and gives the user a recovery option.

This PR is intentionally a minimum-impact fix for the crash. Extending lazygit to actually open a worktree of a bare repo (which is the deeper feature the reporter asks for) is a separate larger change.