Collapse tool-call details by default in Expert chat

Tool-call output is too verbose for an end-user experience. Each call expands to full request/response detail, drowning out the agent's actual narrative response.

Scope:
- Hide tool-call request/response detail by default
- Show a one-line summary per tool call (action name, target, status)
- Provide an expand control to reveal the full payload on demand
- Keep verbose mode available for developer / debug contexts