Batch-update the cast (voices + avatars) on a table read artifact.

Batch-updates the cast on the table read backing this table_read artifact in one call, in place. Each entries item targets one character and may reassign its voice (voiceId / voiceName / gender / provider), request an avatar re-render (regenerateAvatar: true, with an optional avatarRefinement art-direction nudge), or both. A top-level avatarStyle restyles ALL portraits (re-renders every character against the new art-direction). Provide at least one entries item OR a top-level avatarStyle — a body with neither is rejected as validation_failed. Voice reassignments apply immediately. Avatar work is async + queue-backed: the response returns the updated voiceMap plus one avatar op { character, status, chatToolJobId } per queued render — poll GET /artifacts/{artifactId}/cast until each character's avatarStatus reaches ready. No new revision — the artifact id and share URLs stay stable, like a voice recast (no charge). Requires Idempotency-Key. Scope: artifact:publish.