Recast a single character's voice on a table read artifact.

Reassigns one character's voice on the table read backing this artifact, in place. The artifact id, share token, and all player URLs remain STABLE — no new revision, no charge. Body: { character, voiceId, voiceName, gender?, provider?, pinToCanon? }. provider is the TTS provider for the voice (e.g. cartesia, openai); omit to infer it (your library voice's own, else the read's, else the configured table-read provider). A voice whose provider retired it is refused (409 voice_retired). THE CAST CANON FOLLOWS: renders (decks, trailers, showcases) prefer the canon voice, so the recast also pins it on the canon person the character names (by name or alias) unless pinToCanon: false. canon names the person pinned. NOTHING IS LOST: when the voice actually changes on a read that has a recording, the previous voice, the voices-only track and the finished mix are kept before the recording is invalidated, and POST /artifacts/{artifactId}/voice/restore puts them back (restore describes what it would restore). A recast to the voice the character already has changes nothing (changed: false). To keep every other line and re-voice only this character in a finished read, use POST /artifacts/{artifactId}/revoice instead. Returns the updated voiceMap (character → voice). The current cast is also readable on manifest.audio.voiceMap via GET /artifacts/{id}. Requires Idempotency-Key. Scope: artifact:publish.