k8s-agent-sandbox-base

This distribution repackages the "k8s-agent-sandbox" Python client from the
Kubernetes SIGs "agent-sandbox" project:

    https://github.com/kubernetes-sigs/agent-sandbox

Portions Copyright The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (see the LICENSE file).

It is a verbatim re-vendor of that client at commit d0a2213
(git describe: v0.5.3-16-gd0a2213), with the following modifications to
k8s_agent_sandbox/sandbox_client.py:

  * Added a `_build_k8s_helper()` factory (default returns `K8sHelper()`) and
    call it from `__init__`, so the Kubernetes helper can be overridden by a
    subclass.
  * `_create_claim()` now returns the helper's created-claim name, and
    `create_sandbox()` adopts that return value.

Both modifications are no-ops for the default Kubernetes path. Every other file
matches the upstream base verbatim. The import package name (`k8s_agent_sandbox`)
is unchanged from upstream.
