v3.45.3 - Publication boundary correction

v3.45.3 is a publication-boundary correction release.

It removes an internal built-in Playbook template from the public package surface and keeps the public product focused on generic Playbook engine, CLI, schema, and metadata-only management capabilities.

This release also hardens the publishing pipeline: source sanitization now runs in internal strict mode, built wheel/sdist artifacts are scanned with maintainer-local private-term rules before publishing, and release evidence must record an artifact-private-scan pass before CI will publish.