fix: single-source __version__ from package metadata (#78)

[Faerkeren]

Closes #78.

Issue validity

Valid. Confirmed the drift firsthand:

• pyproject.toml declared version 1.1.2
• src/haclient/__init__.py exposed __version__ = "0.2.0"

This is exactly the inconsistency the issue called out.

Fix

Took option 1 from the issue's suggested fixes: keep haclient.__version__ (no breaking change for users) but derive it at import time from installed package metadata, so pyproject.toml is the single source of truth.

from importlib.metadata import PackageNotFoundError
from importlib.metadata import version as _pkg_version

try:
    __version__ = _pkg_version("haclient")
except PackageNotFoundError:  # pragma: no cover
    __version__ = "0.0.0+unknown"

Fallback only triggers if the package is not installed (e.g. running from a raw source tree without pip install).

Tests

Added tests/test_packaging.py:

• test_version_matches_package_metadata — asserts haclient.__version__ == importlib.metadata.version("haclient"), preventing future drift.
• test_version_is_non_empty_string — sanity check.

Checks run

• ruff check src tests — pass
• ruff format --check src tests — pass
• mypy src (strict) — pass, no issues in 38 source files
• pytest tests/ --cov=haclient --cov-fail-under=95 — 318 passed, coverage 97.18%

Verified locally:

pkg meta:    1.1.2
__version__: 1.1.2