Persist/read exact HTML source artifacts for custom site versions

User-scoped keys and an existing managed client binding required. Bounded actions: list_client_projects/get_client_project_artifact require sites:read plus work.read/artifacts.read; create_client_project/save_client_project_artifact_version require sites:write plus work.write/artifacts.write. Writes require Idempotency-Key. Save uses artifact_format=html and complete content up to 1MB, project_id,title,params.idempotency_key and provenance {artifact_schema: bamf-visual-artifact/v1, revision: positive integer, optional provider: openai/anthropic/bamf/other, optional credential-free HTTPS source_session_url}. Updates also require real artifact_id and expected_updated_at. Returns canonical artifact_id/version_id/content_sha256. Use exact saved HTML and those IDs in create_visual_artifact_site_version; it validates persisted content/hash/provenance. Library biz_artifacts are not interchangeable. MCP: bamf.list_site_projects/create_site_project/get_site_artifact/save_site_artifact.