test: cover build_archive and add it to the ruff scope

build_archive.py had no lint or test coverage, which is how the obsolete
requirements/pyproject mirror check slipped through unnoticed. Close that gap:

- Add tests/test_build_archive.py: a network-free smoke test that runs the
  manifest check, dependency parsing, tarball build, and re-verification, and
  asserts the moved docs/ files, LICENSE, and package sources are packaged.
- Lint build_archive.py in both the local gate (scripts/check.sh) and the CI
  workflow; fix the one issue this surfaced (unused variable py_bin).
- List the new test in the REQUIRED_FILES manifest.

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

build_archive.py

@@ -72,6 +72,7 @@ REQUIRED_FILES = [
     "tests/test_http_ops.py",
     "tests/test_lock_ops.py",
     "tests/test_actions.py",
+    "tests/test_build_archive.py",
     "scripts/smoke.sh",
     "docs/BEDIENUNGSANLEITUNG.md",
     "docs/INSTALL_FROM_ARCHIVE.md",
@@ -285,7 +286,6 @@ def smoke_test_install(output_path: Path) -> None:
         venv_dir = tmp_path / "venv"
         venv.EnvBuilder(with_pip=True, clear=True).create(venv_dir)
         pip_bin = venv_dir / "bin" / "pip"
-        py_bin = venv_dir / "bin" / "python"
         llamacppctl_bin = venv_dir / "bin" / "llamacppctl"
 
         result = subprocess.run(