Remove a public ATProto identity

Let a verified profile steward remove the current public ATProto relation while retaining its audit history. The global DID and every account-control relationship remain intact, so this profile action cannot disconnect or transfer the external account.

Use this identity operation for a signed-in person's external ATProto connections or their verified public-profile representation. Keep account control, profile stewardship, and workspace membership separate when interpreting or changing these relationships.