Reverts the label-based deletion approach — resources created by older
laconic-so lack labels, so label queries return empty results. Namespace
deletion is the only reliable cleanup.
Adds _wait_for_namespace_gone() so down() blocks until the namespace
is fully terminated. This prevents the race condition where up() tries
to create resources in a still-terminating namespace (403 Forbidden).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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