Plumb --delete-namespace through the CLI (stop, down), the
down_operation, the Deployer abstract method, and both k8s /
compose implementations. When set, k8s down() calls the existing
_delete_namespace() + _wait_for_namespace_gone() after label-
based resource deletion, restoring the old behavior for the
teardown case. Compose mode ignores the flag.
Default remains False, so normal stop/restart still keep the
namespace Active (Part B behavior).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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