docs: example notebooks and API reference

[ddri]

The SDK currently has a README and CONTRIBUTING.md but no worked examples or API reference. This limits discoverability and onboarding, especially for unitaryHACK contributors.

What's needed

Example notebooks (examples/)

Jupyter notebooks covering common use cases:

• Bell state + local execution — the simplest possible end-to-end example
• VQE with gradient-free optimiser — COBYLA optimisation loop using @task/@workflow to parallelise Pauli measurements
• Multi-backend benchmark — run the same circuit on Local, Braket SV1, and IBM, compare results
• Circuit conversion roundtrip — show Circuit → Qiskit → Circuit, Circuit → Braket → Circuit, etc.
• Parameter sweep — use @workflow to fan out over a range of rotation angles in parallel

API reference

Auto-generated reference docs (e.g. via Sphinx or pdoc) covering:

• marqov.circuits.Circuit — all gates, converters, importers
• marqov.executors — each executor, config classes, ExecutionResult
• marqov.workflows — @task, @workflow, WorkflowDispatch
• marqov.simulation.noise — NoiseModel, noise channels

Notes

• Notebooks should run without cloud credentials (use LocalExecutor or mock cloud calls where needed)
• API reference should be auto-generated from existing docstrings — the inline docs are already thorough

[Forage409]

Opened a small documentation foundation PR in #35: MkDocs + mkdocstrings API reference pages, a credential-free Bell-state local execution walkthrough, and a runnable example script. I kept it reviewable as a first step toward the broader examples/API-reference request.