Initial commit: organized project structure for student handoff

Reorganized flat 41-file directory into structured layout with:
- scripts/ for Python analysis code with shared config.py
- notebooks/ for Jupyter analysis notebooks
- data/ split into raw/, metadata/, processed/
- docs/ with analysis summary, experimental design, and bimodal hypothesis tutorial
- tasks/ with todo checklist and lessons learned
- Comprehensive README, PLANNING.md, and .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,32 @@
+# Large data files (reproducible from raw DBs)
+data/raw/*.db
+data/processed/*.csv
+
+# Generated figures (reproducible from scripts)
+figures/*.png
+
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.venv/
+venv/
+env/
+*.egg-info/
+dist/
+build/
+
+# Jupyter
+.ipynb_checkpoints/
+
+# IDE
+.vscode/
+.idea/
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Claude Code
+.claude/