@cloudflare/voice: preserve active voice sessions across Worker deployments

## Description

Deploying a Worker while an `@cloudflare/voice` session is active disconnects the browser and ends the voice
session.

## Reproduction

1. Create a voice agent using `withVoice(Agent, ...)`.
2. Connect with `VoiceClient`.
3. Start a voice call.
4. Run `wrangler deploy`.
5. The active voice session disconnects and cannot resume.

## Expected behavior

After deployment, the client reconnects to the same Durable Object/session and continues the call, preserving
relevant transcript and conversation state.

## Environment

- `@cloudflare/voice`: 0.2.1
- `agents`: 0.14.3
- `wrangler`: 4.98.0