[codex] Fix agent mode tray mute sync

[rogerchappel]

Summary

• keep agent-mode mic/audio mute changes synchronized with the tray in the same update batch
• reset tray playback and mute state when entering or exiting agent mode
• route both normal and immersive VoiceAgent mic controls through the shared sync handler

Root Cause

VoiceAgent deactivation updated local agent mute state first, while the tray-to-agent sync effect still saw stale tray values in the same render cycle and wrote the old values back. That feedback caused flickering and could trigger React maximum update depth errors.

Verification

• git diff --check
• pnpm typecheck
• pnpm lint:check (passes with existing warnings)
• pnpm build (pre-push hook; passes with existing Turbopack NFT warnings)
• local browser smoke against http://127.0.0.1:3000/chat reached the unauthenticated setup screen with no console errors; agent-mode interaction was not manually reproduced because this clean worktree has no signed-in user/runtime state

Risk

Medium: touches chat agent-mode and tray voice state synchronization only.