replace JSON messages with protobuf messages

[chenghao-mou]

Description

Replace the JSON messages with Protobuf messages in Remote Session
Replace client message handler with Session Host

Changes Made

• Replace the JSON messages with Protobuf messages in Remote Session
• Replace client message handler with Session Host

Pre-Review Checklist

• Build passes: All builds (lint, typecheck, tests) pass locally
• AI-generated code reviewed: Removed unnecessary comments and ensured code quality
• Changes explained: All changes are properly documented and justified above
• Scope appropriate: All changes relate to the PR title, or explanations provided for why they're included
• Video demo: A small video demo showing changes works as expected and did not break any existing functionality using

CleanShot.2026-03-17.at.15.25.58.mp4

Testing

• Automated tests added/updated (if applicable)
• All tests pass
• Make sure both restaurant_agent.ts and realtime_agent.ts work properly (for major changes)

Tested locally with the playground changes

Additional Notes

Dependency on

• add livekit_agent_simulation service, agent remote session proto & cli dev proto protocol#1404
• use remote session protobuf agents-playground#197

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Note to reviewers: Please ensure the pre-review checklist is completed before starting your review.

[changeset-bot]

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Latest commit: 93dfe9d

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