dev.cocore.account.revokeApiKey

Revoke one of the authenticated account's API keys. The key stops authenticating immediately, but the row is retained with `revokedAt` set so it stays visible in listApiKeys as a revoked key (audit trail). Use deleteApiKey to remove it entirely. Scoped to the caller's DID — you cannot revoke another account's key. Idempotent: revoking an already-revoked or unknown key returns `revoked: false`.