fix: derive __version__ from package metadata (#2)

The publish workflow's `uv version --bump` step only edits
`pyproject.toml`, but `__version__` was a hand-kept constant in
`__init__.py`. After the v0.2.0 release the wheel's metadata said
`0.2.0` while `commonlid.__version__` and every `summary.json`'s
`commonlid_version` field stayed at `0.1.0`.

Make `pyproject.toml` the single source of truth: read the version
from `importlib.metadata.version("commonlid")` at import time, with a
sentinel fallback for un-installed source-tree imports. Lives in a new
`_version.py` to keep `__init__.py` lint-clean (RUF067 forbids
runtime statements there).

Add a regression test asserting `commonlid.__version__` equals
`importlib.metadata.version("commonlid")` so any future drift is
caught by the standard gate run instead of in production.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: malteos

src/commonlid/__init__.py

@@ -6,6 +6,7 @@
 # model's ``load()``), so this stays cheap.
 from commonlid import datasets as _tasks  # noqa: F401
 from commonlid import models as _models  # noqa: F401
+from commonlid._version import __version__
 from commonlid.core.lid_dataset import LIDDataset, PrivateDatasetAccessError
 from commonlid.core.lid_model import LIDModel, LIDPrediction
 from commonlid.core.registry import (
@@ -19,8 +20,6 @@
 from commonlid.evaluation.evaluator import Evaluator
 from commonlid.evaluation.results import Result
 
-__version__ = "0.1.0"
-
 __all__ = [
     "Evaluator",
     "LIDDataset",

src/commonlid/_version.py

@@ -0,0 +1,16 @@
+"""Single source of truth for the package version.
+
+Read from the wheel metadata so it can never drift from ``pyproject.toml``.
+The fallback only fires for source-tree imports that were never installed
+(e.g. ``PYTHONPATH=src python …``).
+"""
+
+from __future__ import annotations
+
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as _pkg_version
+
+try:
+    __version__ = _pkg_version("commonlid")
+except PackageNotFoundError:  # pragma: no cover
+    __version__ = "0.0.0+unknown"

tests/unit/test_cli_stub.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+from importlib.metadata import version as _pkg_version
 
 from typer.testing import CliRunner
 
@@ -16,6 +17,16 @@ def test_version() -> None:
     assert __version__ in result.stdout
 
 
+def test_version_matches_package_metadata() -> None:
+    """``commonlid.__version__`` must track the wheel's installed metadata.
+
+    Catches the failure mode where the publish workflow bumps
+    ``pyproject.toml`` but a hand-kept version constant inside the package
+    drifts. The two should never diverge at runtime.
+    """
+    assert __version__ == _pkg_version("commonlid")
+
+
 def test_list_models_json_contains_known_models() -> None:
     result = runner.invoke(app, ["list-models", "--json"])
     assert result.exit_code == 0