Sets the block policy for one hostname. This changes edge serving outside Studio: requests attributed to a blocked hostname (by the storefront URL the Hydrogen SDK declares) are refused this project's content. It is containment, not authentication.

• hostname must be a bare canonical hostname (no scheme, path, port or credentials, at most 253 characters); anything else is refused with 400 rather than reinterpreted.
• confirm must equal the hostname (lowercase); a missing or different value is a 400.
• Desired-state write: blocked sets the state, so a replayed request converges instead of toggling.
• The change reaches the edge within propagationSeconds.
• 503 when the policy service is unavailable; nothing changed.

Required scope: project:manage