docs: add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Python template for libraries and applications with Docker packaging. Uses `uv` for dependency management, `ruff` for linting/formatting, and `pytest` for testing.
+
+## Common Commands
+
+```bash
+# Install uv and dependencies
+make install
+
+# Run tests
+make test
+
+# Run tests with optional markers
+uv run pytest --optional
+
+# Run a single test file
+uv run pytest tests/test_trivial.py
+
+# Run a single test
+uv run pytest tests/test_trivial.py::test_print_version
+
+# Lint and format
+make ruff
+
+# Run pre-commit hooks on all files
+make hooks
+
+# Run the API locally (port 7000)
+uv run python template/api.py
+
+# Build and run Docker container
+make docker
+```
+
+## Architecture
+
+- `/template`: Main Python package
+  - `main.py`: CLI entry point using Typer, exposes version via `main` console script
+  - `api.py`: FastAPI application with `/` (version check) and `/predict` endpoints
+- `/tests`: Pytest test suite
+  - `conftest.py`: Custom `--optional` flag for marking optional tests with `@pytest.mark.optional`
+
+## Code Style
+
+- Python 3.9-3.12 compatible
+- Use `from __future__ import annotations` for union type syntax (`A | B`)
+- Docstrings follow NumPy convention
+- Ruff rules: pycodestyle (E), Pyflakes (F), pyupgrade (UP), flake8-bugbear (B), flake8-simplify (SIM), isort (I), pydocstyle (D)
+- mypy strict mode enabled for the `template` package
+
+## Dependencies
+
+- Add dependencies: `uv add <package>`
+- Add dev dependencies: `uv add --dev <package>`
+- Upgrade all: `uv lock --upgrade`