Make creative rewriting optional #914

Problem

Creative HTML is always sanitized and rewritten before it is returned from the auction path. Operators cannot opt out when a deployment needs the original creative markup.

Proposal

Add an operator-facing configuration option that controls creative rewriting. It should default to the current enabled behavior for backwards compatibility.

When disabled, winning creative HTML should be delivered without the creative URL-rewriting pass. Define and document whether sanitization remains mandatory or is controlled separately, with security implications made explicit.

Acceptance criteria

• A documented config option controls creative rewriting.
• The default preserves current behavior.
• The auction creative delivery path honors the option.
• Tests cover enabled (current behavior) and disabled behavior.
• Configuration and creative-processing documentation are updated.