Scaffold Python project with pyproject.toml and pytest

Add a src/-layout package (shard_wiki), hatchling build config, pytest
and ruff configuration, and smoke tests proving the import path and test
harness are wired correctly. Update CLAUDE.md with real build/test commands.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_package.py

@@ -0,0 +1,17 @@
+"""Smoke tests for the package scaffold.
+
+These exist to prove the test harness and import path are wired correctly.
+Replace/extend them as the domain model (shards, adapters, projections,
+overlays — see INTENT.md) takes shape.
+"""
+
+import shard_wiki
+
+
+def test_package_imports():
+    assert shard_wiki is not None
+
+
+def test_version_is_exposed():
+    assert isinstance(shard_wiki.__version__, str)
+    assert shard_wiki.__version__