Migrate build system from setuptools to hatchling

[Copilot]

Replaces setuptools with hatchling as the PEP 517 build backend. Version continues to be derived from git tags via hatch-vcs (equivalent to previous setuptools-git-versioning behavior).

Changes

pyproject.toml:

• Build system: setuptools → hatchling>=1.28.0 + hatch-vcs>=0.5.0
• Versioning: [tool.setuptools-git-versioning] → [tool.hatch.version] with VCS source
• Removed: [tool.setuptools] and [tool.setuptools.package-data] sections (hatchling auto-includes git-tracked files)

CI workflow:

• Added uv build step to verify package builds successfully

Version derivation remains unchanged: v1.2.3 tag produces 1.2.4.dev0+g<sha> for subsequent commits.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• astral.sh
  • Triggering command: /usr/bin/curl curl -LsSf REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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