Self-Review Checklist:

- [X] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [X] Performance impact has been considered and is acceptable

Updated `CommitDataReader::read` from single SHA to batched
input/output.
`run_commit_data_reader` is designed to process requests in batches, but
`CommitDataReader::read` previously only sent one SHA per call. So in
practice, commit data was effectively processed one-by-one from the
caller path.


The temporary debug logs show that batching was not performed
previously.

before:
<img width="607" height="154" alt="image"
src="https://github.com/user-attachments/assets/4f9d9041-6209-426f-be44-f28449504c80"
/>

after:
<img width="632" height="121" alt="image"
src="https://github.com/user-attachments/assets/43b349f3-7685-4786-af1e-2a640cdf8ccd"
/>


Release Notes:

- N/A

---------

Co-authored-by: Anthony Eid <56899983+Anthony-Eid@users.noreply.github.com>
Co-authored-by: Anthony Eid <anthony@zed.dev>