Discards everything one POST /locations-directory/articles/bulk run wrote — identified by its version_token — and restores whatever version of each affected link tuple it superseded. A tuple the run created (rather than versioned) has nothing to restore, so it is simply left without a live article.

Idempotent: calling this again with the same version_token after it has already been rolled back is a no-op that returns {"discarded": 0, "restored": 0}, which also makes it safe for a caller (such as a retried workflow step) to call more than once. An unknown or already-rolled-back version_token is likewise {"discarded": 0, "restored": 0} rather than an error — the token is opaque and is not validated against anything.