[agent test] Use numeric user ID instead of email for context.user_id

[jennsun]

Summary

• Pass session.user.id (the Databricks numeric user ID from X-Forwarded-User header, e.g. 4255605719359984@2850744067564480) instead of session.user.email as the context.user_id sent to the agent backend
• This avoids exposing email addresses in agent memory namespaces and Lakebase store keys
• The numeric ID is the stable Databricks identity and is always available (email is optional per the X-Forwarded-Email header)

Test plan

• Deploy agent template with long-term memory, verify context.user_id in backend logs shows numeric ID
• Verify memory save/retrieve still works with the numeric ID namespace
• Verify chat history and session continuity are unaffected

🤖 Generated with Claude Code