## Summary

- Allows Git Graph search to match abbreviated or full commit hashes
when the query looks like a SHA.
- Keeps the existing message search behavior for non-hash queries.
- Mirrors the hash search heuristic in the fake git backend and adds
GPUI coverage for hash and message search.

<img width="1912" height="1241" alt="image"
src="https://github.com/user-attachments/assets/903b438e-baa8-4447-95dc-faf321bca6a5"
/>


## Test Plan

- `cargo fmt --check --package git_ui`
- `cargo -q test -p git_ui
test_git_graph_search_matches_commit_hash_prefix -- --nocapture`
- `./script/clippy -p git_ui`

## Suggested .rules additions

- N/A

Release Notes:

- Improved Git Graph search to find commits by abbreviated or full hash.