Redact (soft-delete) the donor note on one of the authenticated merchant's orders KAN-862 takedown path: hides a guest-supplied tip / donation note from every surface. The original text is RETAINED server-side (soft-delete) for a possible exposure / legal review; no "[redacted]" placeholder is shown. Idempotent (an order with no note, or an already-redacted note, is a no-op). 403-family error if the order belongs to another merchant (ownership is asserted server-side).