Add pyproject.toml packaging and pytest suite

- pyproject.toml: setuptools build, deps (requests), dev extra (pytest),
  pytest config with opt-in `live` marker
- tests/: 95 offline tests locking every series-ID encoding against
  known-good IDs (regression guard for the JOLTS/OES/ECI/productivity/QCEW
  fixes), plus a live API smoke test behind `-m live`
- README: install-as-package + test instructions; drop the now-resolved
  "no packaging"/"no tests" limitations
- gitignore build/test artifacts

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -0,0 +1,31 @@
+[build-system]
+requires = ["setuptools>=61"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "bls-data"
+version = "0.1.0"
+description = "Dependency-light Python client for the U.S. Bureau of Labor Statistics (BLS) API, with pre-built series-ID builders."
+readme = "README.md"
+requires-python = ">=3.9"
+license = { text = "MIT" }
+authors = [{ name = "Dave Boyd", email = "dave@tiggr.org" }]
+keywords = ["bls", "economics", "labor-statistics", "cpi", "jolts", "unemployment", "wages"]
+dependencies = ["requests>=2.28"]
+
+[project.optional-dependencies]
+dev = ["pytest>=7"]
+
+[project.urls]
+Homepage = "https://gitea.doesworks.net/giteaadmin/bls-data"
+
+[tool.setuptools]
+packages = ["bls_client", "bls_client.queries"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+markers = [
+    "live: hits the live BLS API (needs network + BLS_API_KEY; deselected by default)",
+]
+# Live tests are opt-in: run `pytest -m live` to include them.
+addopts = "-m 'not live'"