Fix all broken README/docs examples and unify the version across 4 locations #124

Part of #108 · Phase 5 · label: documentation

Problem

Every cloud configuration example in README.md raises on its first line. configure() has no pass-through for unknown keys — config.py:262 raises ValueError(f"Unknown configuration parameter: {key}") — and the README uses unprefixed names that do not exist.

Other broken examples:

• @cluster(provider='lambda_cloud') / provider='huggingface_spaces' -> ValueError: Unsupported cloud provider. executor_core.py:63 accepts only ["lambda","aws","azure","gcp","huggingface"]. The decorator's own docstring (decorator.py:57) uses the correct short names — the README does not.
• monitor.get_cost_optimization_recommendations() -> TypeError: missing 2 required positional arguments. Signature is (self, resource_usage, cost_estimate) (cost_monitoring.py:126).
• @cluster(provider='aws', cluster_type='kubernetes', cluster_name=...) — cluster_type is not a cluster() parameter; it lands silently in **kwargs and configures nothing. machine_type, vm_size, space_hardware are likewise silently absorbed.
• README claims "Zero use of @patch, Mock(), or simulations" — 60 of 240 test files use mocks, 2,513 occurrences, including 3 inside tests/real_world/.

MIGRATION.md is also wrong: it lists from clustrix import ClusterConfig under "These imports continue to work unchanged" — that symbol is not in clustrix/__init__.py at all. It also quotes a testpaths value and marker list that no longer match pyproject.toml.

Version drift — four locations, two values

Both setup.py and pyproject.toml declare name/version/deps independently. The PEP 517 build uses pyproject.toml and silently ignores setup.py, so the metadata you read may not be the metadata that installs.

Docs site

• docs/source/api/notebook_magic.rst autodocs ClusterConfigWidget — no such class exists. The real ones are EnhancedClusterConfigWidget (notebook_magic_widget.py:35) and ModernClustrixWidget (modern_notebook_widget.py:24).
• docs/source/index.rst:23 lists only SLURM/PBS/SGE/Kubernetes/SSH — no cloud — contradicting the README's cloud claims.
• Local sphinx-build fails at conf.py:34 on ModuleNotFoundError: No module named 'sphinx_wagtail_theme' (environment-only; RTD installs it).

Acceptance criteria

• Every code example in README.md is executed by a doc test in CI. This is the only durable fix — prose drifts, executed examples cannot.
• Claims are reduced to what actually works. Anything a Phase 3 issue has not yet fixed is marked clearly as unsupported/experimental rather than advertised.
• One source of truth for the version; all four locations agree. Prefer deleting setup.py.
• MIGRATION.md corrected or retired
• docs/ autodoc targets resolve; index.rst and README.md agree on the supported backend list
• The "no mocks" claim is either made true (Phase 2) or removed