Client event tool changes pt-BR custom voice accent/prosody instead of failing clearly

The README says client events are supported on avatars that use a preset voice, and that custom voice avatars do not currently support client events.

However, when creating a realtime session for a custom avatar using a custom pt-BR voice, passing a minimal client_event tool is accepted by the session create flow, but the avatar
voice/accent changes immediately.

Expected:
For custom voice avatars, either:

1. reject client_event tools clearly at session creation, or
2. ignore unsupported client-event tools without changing the configured custom voice/accent.

Actual:
The session starts, but the custom Brazilian Portuguese voice changes to a noticeably foreign/non-native accent.

Minimal tool payload:

"tools": [
  {
    "type": "client_event",
    "name": "registrar_evento",
    "description": "Use esta ferramenta apenas para registrar no console que a ferramenta client_event foi chamada.",
    "parameters": []
  }
]

A/B result in runway-characters-meet:

• omitted tools: correct pt-BR custom voice/accent
• minimal client_event tool: accent/prosody changes
• omitted tools again: correct pt-BR custom voice/accent returns

Related issue:
https://github.com/runwayml/runway-characters-meet/issues/2

Start with the README's statement about client events and preset versus custom voices, then reproduce the A/B behavior using the minimal client_event payload during realtime session creation. Trace the session-create flow and any client-event validation or forwarding it exposes. Done means unsupported tools are clearly rejected or ignored without changing the configured custom pt-BR voice and accent.