Transcribe stream deadlock fixed; errored responses stay loadable

Patch Changes

• ac01b79: Allow validating assistant UI messages with empty parts so persisted errored responses remain loadable.
• 2696562: experimental_streamTranscribe result promises now resolve without consuming fullStream: accessing any result promise consumes the stream internally. Previously await result.text alone deadlocked on transform backpressure. Because live transcription streams can be unbounded, fullStream is explicitly single-consumer (no replay buffering): access it once, before any result promise, when both stream parts and final results are needed.
• Updated dependencies [31c7be8]
• Updated dependencies [4d096f6]
  • @ai-sdk/provider-utils@5.0.10
  • @ai-sdk/gateway@4.0.20