feat(integrations): Add LiveKit runner for voice and telephony

[allen-stephen]

Summary:
ADK had no first-party connector for realtime media, so reaching a live agent over WebRTC or SIP meant hand-rolling a bridge onto LiveRequestQueue. LiveKitRunner takes an already-connected rtc.Room and bridges it to an unmodified Runner over the transport-agnostic LiveRequestQueue -> run_live() -> Event contract, publishing on LiveKit's standard channels so their client SDKs render an ADK agent unchanged.

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.