[Doc]Clarify ray.shutdown() behavior for local vs remote clusters

[OneSizeFitsQuorum]

• Update the docstring for ray.shutdown() in python/ray/_private/worker.py to clarify:
  • When connecting to a remote cluster via ray.init(address="xxx"), ray.shutdown() only disconnects the client and does NOT terminate the remote cluster
  • Only local clusters started by ray.init() will have their processes terminated by ray.shutdown()
  • Clarified that ray.init() without address argument will auto-detect existing clusters
• Add documentation note to doc/source/ray-core/starting-ray.rst explaining the same behavior difference
• Review the changes via code_review
• Run codeql_checker for security scan (no code changes requiring analysis)

[gemini-code-assist]

Code Review

This pull request clarifies the behavior of ray.shutdown() in both the API docstring and the core documentation. The changes are clear and accurate. I have a couple of suggestions to make the explanation even more explicit for users who call ray.init() without arguments, which is a very common use case.

I am having trouble creating individual review comments. Click here to see my feedback.

doc/source/ray-core/starting-ray.rst (86)

To improve clarity, it would be helpful to explicitly mention that ray.init() with no arguments can also connect to an existing cluster. This is a very common use case and adding it to the examples would make the documentation more complete.

  * If you connected to an existing cluster (e.g., via ``ray.init()`` when a cluster is already running, ``ray.init(address="auto")``, or ``ray.init(address="ray://<ip>:<port>")``), ``ray.shutdown()`` only disconnects the client -- it does **not** shut down the remote cluster.

python/ray/_private/worker.py (2031-2033)

For better clarity, let's explicitly mention the case where ray.init() without arguments connects to an existing cluster. This makes the documentation more comprehensive for this common scenario.

        * If you connected to an existing cluster (e.g., by calling
          ``ray.init()`` when a cluster is already running, using
          ``ray.init(address="auto")``, or ``ray.init(address="ray://<ip>:<port>")``),
          ``ray.shutdown()`` will only disconnect the client from the cluster.

[edoakes]

Thank you!