Week5/m2 myers diff

[Saanvi521]

Summary

• Implemented Myers diff
• Added line details to diff_working_tree_vs(tree_hash)
• Added minigit diff: HEAD tree vs working files; unborn HEAD -> empty tree.
• Added all relevant tests

Validation

• scripts/quality-check.sh
• Manual testing, if applicable:

Checklist

• The change is focused and easy to review.
• Tests were added or updated for behavior changes.
• Documentation was updated for user-facing or setup changes.
• No secrets, generated artifacts, or local-only files are included.

Notes for Reviewers