Add docstring examples to rocky-sdk RockyClient core methods

[hugocorreia90]

rocky-sdk is published on PyPI, but sdk/python/src/rocky_sdk/client.py has zero worked examples in its docstrings across the ~20 public RockyClient methods. New users discovering the SDK have to read the source to learn how to construct a client and call it. #482 added Example: blocks to the Dagster health helpers; this is the same shape on the canonical, more-used surface.

Scope (capped — do not document all 20 methods)

Add a Sphinx-style Example: block to the four core methods only:

1. RockyClient.discover — engine/crates/.../client.py → sdk/python/src/rocky_sdk/client.py:666
2. RockyClient.plan — sdk/python/src/rocky_sdk/client.py:687
3. RockyClient.apply — sdk/python/src/rocky_sdk/client.py:709
4. RockyClient.run — sdk/python/src/rocky_sdk/client.py:721

Each example should show constructing RockyClient(...) and using the returned typed model. Pure docstring work — no logic or signature changes.

Code refs

• sdk/python/src/rocky_sdk/client.py — the four method definitions above
• Add docstring examples to public functions in dagster_rocky.health #482 (dagster health Example sections) for the docstring style to mirror

Acceptance criteria

• Each of the four methods gains an Example: block with runnable example code
• Examples import RockyClient from rocky_sdk (the public path)
• ruff check sdk/python is clean
• pytest sdk/python is green (no regressions)

Effort

2 hours.