Migrate build system to pyproject.toml with hatchling

[dguido]

Summary

• Replace setup.py with pyproject.toml as single source of truth
• Use hatchling as build backend (simpler than setuptools)
• Add PEP 735 dependency-groups for dev dependencies
• Add uv.lock for reproducible builds

Changes

File	Change
pyproject.toml	Full package config, deps, entry points, tool settings
setup.py	Deleted (migrated to pyproject.toml)
Makefile	Updated commands with uv support
.gitignore	Updated patterns
uv.lock	Lockfile for reproducible builds

Installation

# Traditional pip (still works)
pip install -e ".[dev]"

# Modern uv (10-100x faster)
pip install uv
uv sync --group dev

Why hatchling?

• Simpler configuration than setuptools
• Native pyproject.toml support
• No setup.py/setup.cfg needed
• Fast builds

Testing

• ✅ pip install -e . works
• ✅ uv sync works
• ✅ All 14 console scripts available
• ✅ uv build creates valid wheel

Part of

This is PR 1 of 4 splitting up #2768 (modernize-linting-and-config) into reviewable chunks.

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