Backend was returning fields like 'author', 'email', 'date' but frontend
expected 'author_name', 'author_email', 'author_date'. Also 'branches' and
'tags' were separate but frontend expects unified 'refs' array.
- Update _commit_to_dict to return frontend-compatible field names
- Add graph_symbol and graph_depth for commit graph display
- Update get_commit_detail to return matching field names
- Include diff as top-level field for detail view
Fusion
d4b52668aa