chore: add Codex and agent workflow foundation

.gitignore

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+# OS / editor
+.DS_Store
+Thumbs.db
+*.swp
+*.swo
+.idea/
+.vscode/
+
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+.python-version
+
+# Virtualenvs
+.venv/
+venv/
+env/
+
+# Packaging / build
+build/
+dist/
+*.egg-info/
+.eggs/
+pip-wheel-metadata/
+
+# Testing / coverage
+.pytest_cache/
+.coverage
+.coverage.*
+htmlcov/
+.tox/
+.nox/
+
+# Type check / lint caches
+.mypy_cache/
+.ruff_cache/
+.pyre/
+
+# Django
+db.sqlite3
+db.sqlite3-journal
+media/
+staticfiles/
+local_settings.py
+
+# Environment / secrets
+.env
+.env.*
+!.env.example
+
+# Logs / pid
+*.log
+*.pid
+
+# Jupyter
+.ipynb_checkpoints/
+
+# Codex / agents local-only state
+.codex/tmp/
+.codex/cache/
+
+# Project runtime data
+data/
+tmp/