fix(memory-proxy): allow members to select team-visible agents

[guomengjia618-dot]

Summary

• Query active agents at team scope during CodeBuddy session initialization.
• Allow team members to select agents they own and agents with visibility="team".
• Keep private agents owned by other team members hidden.
• Add a regression test covering owned private, team-visible, and other private agents.

Root cause

CodeBuddy session initialization passed the current user ID to MetadataClient.listAgents, which added an owner_user_id filter to the team query. Team-visible agents created by an admin or another member were therefore omitted, causing session initialization and downstream memory injection to be bypassed.

Impact

Team members can now select shared agents during CodeBuddy session initialization without gaining access to another member's private agents.

Testing

• npm test in MemoryProxy
• Targeted strict TypeScript check for the new selector and regression test

Fixes #924