Add support for namespace description

[daehan-temporal]

What was changed

• Added description field to

temporal cloud namespace create

• Added namespace description subcommand

temporal cloud namespace description get
temporal cloud namespace description set

Why?

Checklist

1. Closes

2. How was this tested:

3. Any docs updates needed?

Can actually merge once temporalio/cloud-sdk-go#64 lands (sdk-go v0.18)

---

Note

Low Risk
Additive CLI and SDK bump; set follows the same get-update-async pattern as other namespace field commands with confirmation prompts.

Overview
Adds namespace description support across Temporal Cloud namespace commands, backed by a bump of go.temporal.io/cloud-sdk from v0.16.0 to v0.18.0.

temporal cloud namespace create gains an optional --description flag (up to 255 printable ASCII characters plus whitespace), wired through CreateNamespace into NamespaceSpec.Description. Namespace list output now includes Description in spec fields.

A new temporal cloud namespace description command group provides get (structured JSON of namespace + description) and set (clone spec, prompt via PromptApply, UpdateNamespace with async polling, optional resource version / async operation id, empty --value clears the field).

Command definitions are declared in commands.yml with generated cobra wiring in commands.gen.go; behavior lives in commands.namespace.description.go with unit tests for create and description get/set.

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[khisakuni]

Just a nit on the helper text. I think it's sufficient to say it's the description of the namespace and I think saying it describes the purpose of the namespace is maybe presumptuous since users can put whatever they want there.