Add fan-out reference implementation

[jacobthebanana]

PR Type

Feature

Short Description

Add async fan-out reference implementation for handling second-order tasks efficiently at scale.

Example task: identify conflicts between information presented across 50 document chunks.

Tests Added

Test manually:

uv run --env-file .env src/2_frameworks/2_multi_agent/fan_out.py \
--source_dataset laliyepeng/test-cra-dataset \
--num_rows 10 \
--output_report report.md

Example output: (gist URL)

[jacobthebanana]

Ready for review. As expected, this setup can consume a lot of tokens. The example below shows an attempt to identify conflicts between 50 CRA document chunks, producing this massive markdown report.

LangFuse traces:

• $O(n^{2})$ fan-out
• $O(n)$ summarize/review