fix(knowledge): use primary agent for archival memory instead of sleeptime agent
- Remove sleeptime_agent_id checks and error messages
- Use coAgent.id directly for all archival memory operations
- Apply to loadPassages, createPassage, deletePassage, and modifyPassage
- Fixes "Sleeptime agent not available" error in Knowledge > Archival Memory
- Archival memory now works with the primary Co agent