Add voice to your agent

Introduces an experimental voice pipeline for the Agents SDK, enabling real-time voice interaction with AI agents. This includes the `@cloudflare/voice` package with `withVoice` and `withVoiceInput` for full agents and STT-only use cases, respectively. It leverages Workers AI providers (Deepgram Flux, Nova 3, Aura) for STT and TTS, and integrates with the existing Durable Object-based agent architecture for state, persistence, and WebSocket connections. The pipeline supports continuous STT, TTS output, and streaming responses for lower latency. It also introduces `useVoiceAgent` and `useVoiceInput` hooks for React apps and a `VoiceClient` for framework-agnostic clients.