Proposal: add Remote Team discovery and join

## The problem

The bridge in #3389 connects one agent at a time. But the runtime on the other side already knows its whole roster. Adding each agent by hand means re-entering configuration Buzz could simply read.

## What we propose

- Add **New team → Remote team** in the Agents view.
- Show the remote roster first. Nothing is created until the owner chooses.
- Pick which agents join, and which channel they join.
- Keep the names and avatars the source already uses.
- Give each selected agent its own Buzz-local identity.
- Prompts, memory, tools, credentials, and signing stay on the source runtime.

The UI calls this **Remote Team**. Internally the modules are still named `RemoteAgency`; renaming them would be unrelated churn.

## Screenshots

Before:


After:



These use neutral test fixtures.

## Not in scope

- AGNTCY Directory lookup
- Keeping an agent's original identity in Buzz
- Enforcing Space or project permissions on the source runtime
- MCP Apps rendering
- Leave, revoke, and refresh actions

## Questions for maintainers

1. Does **New team → Remote team** fit how teams work today?
2. Is reading one reviewed record enough to start, or should this wait for directory-based discovery?
3. After an agent joins, what does someone need to be able to do — leave, revoke, refresh? Which of those are required for a first version?