chore: exclude .python-version from package distribution

[mldangelo]

Summary

Excludes .python-version from the package source distribution. This file is used by pyenv and other version managers for local development but shouldn't be distributed to end users.

Problem

Testing PyPI 0.1.1 revealed that .python-version was still being included in the source distribution:

promptfoo-0.1.1/.python-version  ❌
promptfoo-0.1.1/src/promptfoo/__init__.py
promptfoo-0.1.1/src/promptfoo/cli.py
...

Solution

Add /.python-version to the [tool.hatch.build.targets.sdist] exclude list.

Verification

$ uv build
$ tar -tzf dist/promptfoo-0.1.1.tar.gz | grep "\.python-version"
# No output ✅ Successfully excluded

$ tar -tzf dist/promptfoo-0.1.1.tar.gz
promptfoo-0.1.1/.gitignore
promptfoo-0.1.1/LICENSE
promptfoo-0.1.1/PKG-INFO
promptfoo-0.1.1/pyproject.toml
promptfoo-0.1.1/README.md
promptfoo-0.1.1/src/promptfoo/__init__.py
promptfoo-0.1.1/src/promptfoo/cli.py

Only essential files remain ✅

Impact

• Users: Will no longer receive .python-version when installing from source
• Distribution size: Negligible reduction (tiny file)
• Package quality: Cleaner, more professional distribution

🤖 Generated with Claude Code