[BUG] Cannot stage a conflicted submodule path after rebase

[luisjomen2a]

1. Description

When a rebase in the superproject stops with a conflict on a submodule
gitlink, Git Graph+ cannot mark the submodule path as resolved or continue
the rebase.

The conflict is on the parent repository path. The submodule working tree itself is clean.

Running the equivalent command manually from the superproject works:

git add <my_submodule>

This appears different from PR #34, which fixed rebase state detection when
Git Graph+ is opened directly on a submodule.

2. Steps to Reproduce

1. Open a superproject containing the <my_submodule> submodule in Git Graph+.
2. Start a rebase that produces a conflict on the submodule pointer.
3. Resolve the submodule version manually.
4. Use Git Graph+'s conflict UI to mark <my_submodule> as resolved or continue the rebase.

3. Expected Behavior

Git Graph+ stages the conflicted submodule path in the superproject and
continues the rebase successfully.

4. Actual Behavior

Git Graph+ does not stage the submodule path, or the continue action fails.
Running git add <my_submodule> manually from the superproject works.

Related: #34

5. Screenshots or Logs

N/A

6. Environment

• OS: Ubuntu 24.04
• VS Code version: 1.135.0
• Git Graph+ version: 0.7.3
• Git version: 2.43.0
• Node.js version e.g., 20.19.5

7. Additional Context

The conflict is represented by three mode-160000 index entries for <my_submodule>.
The submodule repository itself is clean.