assistant-ui feat(react): dictation

Behavior: Adds dictation support using SpeechRecognitionAdapter interface. Introduces WebSpeechRecognitionAdapter for browser-based speech recognition. Example integration with ElevenLabs Scribe for real-time transcription.
Components: New components ComposerPrimitive.Dictate , ComposerPrimitive.StopDictation , and ComposerPrimitive.ListeningTranscript for dictation control. Updates ComposerPrimitive.Input to handle input disabling during dictation.
Documentation: Updates README.md to include dictation feature. Adds Dictation.mdx guide and updates Composer.mdx API reference.
Examples: Adds with-elevenlabs-scribe example demonstrating ElevenLabs Scribe integration. Includes API routes for token generation and chat handling in the example.

This PR adds support for dictation and an example with ElevenLabs Scribe v2.

[!IMPORTANT] Adds dictation support with SpeechRecognitionAdapter, including WebSpeechRecognitionAdapter and ElevenLabs Scribe integration, with new components and documentation updates.

Behavior:

Adds dictation support using SpeechRecognitionAdapter interface.

Introduces WebSpeechRecognitionAdapter for browser-based speech recognition.

Example integration with ElevenLabs Scribe for real-time transcription.

Components:

New components ComposerPrimitive.Dictate, ComposerPrimitive.StopDictation, and ComposerPrimitive.ListeningTranscript for dictation control.

Updates ComposerPrimitive.Input to handle input disabling during dictation.

Documentation:

Updates README.md to include dictation feature.

Adds Dictation.mdx guide and updates Composer.mdx API reference.

Examples:

Adds with-elevenlabs-scribe example demonstrating ElevenLabs Scribe integration.

Includes API routes for token generation and chat handling in the example.

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