Managed agent invisible/unresponsive to other community members even after setting "Who can talk to this agent" to Everybody

**Describe the bug**
A managed agent owned by one community member is invisible in another member's @ mention picker in a shared channel, and does not respond to that other member's messages at all — even after explicitly setting the agent's "Who can talk to this agent" option to "Everybody" and restarting the agent.

**Steps to reproduce**
1. User A creates/deploys a managed agent in Buzz Desktop and adds it to a shared channel that User B (a different community member) is also a member of.
2. Confirm the agent responds normally to User A's own @ mentions in that channel.
3. User A changes the agent's "Who can talk to this agent" setting from "Only me" to "Everybody."
4. User A stops and restarts the agent.
5. User B opens the same channel and types @ — the agent does not appear in User B's mention autocomplete; only User B's own agents and human community members show up.
6. User B tries typing the agent's name manually as unresolved literal text, and separately tries posting a plain message with no mention at all — in both cases, the agent never responds.

**Expected behavior**
Once "Who can talk to this agent" is set to "Everybody," any community member in a shared channel should be able to see and interact with the agent — not just its creator.

**Version and platform**
- Buzz version: 0.4.26
- OS: macOS (both users)

**Logs / additional context**
The agent was confirmed working correctly for its creator throughout (holding conversations, making real GitHub commits/PRs) — ruling out the agent itself being offline or broken. Renaming the agent, changing "Who can talk to this agent" to "Everybody," and a full restart were all tried independently, with zero change to the reported symptom in any case.