[divijagv]

Added the optional contributor object (name only) to the trace merged in #107, as suggested in the review.

• One file changed: the datasets(traces): add adversarial multi_agent_delegation trace #107 entry, +4 lines.
• No change to the trace content, 'index.csv' or 'croissant.json' (the index has no contributor column).
• 'python data_validation/run_all_checks.py': 0 failed.