Use small test data files instead of full parquet samples

Create 10-row subsets of entity, interaction, and association
parquet files under tests/data/ (~24KB total vs 90MB originals).
Update test fixtures to use the new location.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: deeenes

tests/conftest.py

@@ -7,7 +7,7 @@
 import pytest
 
 
-SAMPLES_DIR = Path(__file__).parent.parent / 'parquet-samples'
+SAMPLES_DIR = Path(__file__).parent / 'data'
 
 
 @pytest.fixture