IndexNow key rotation causes ~2-day HTTP 403 SiteVerificationNotCompleted window

After rotating an IndexNow API key (even when the new key file is deployed and the _verify_key_location pre-flight passes), submissions return HTTP 403 with error SiteVerificationNotCompleted for approximately 2 days while the search engine side re-verifies the new keyLocation. This is not documented in the IndexNow spec. The correct response is to carry the submission and retry on subsequent runs; the ledger is only written on success so nothing is lost. Observed: key rotated 2026-08-06, first 403 on 2026-08-07, first 200 on 2026-08-08. Do not treat this as an error requiring code changes or key re-rotation.