- When clicking a session card, switch to the correct project and viewMode
  ('chat' for home sessions, 'experts' for expert sessions) instead of only
  setting the active session ID
- Persist session scope via sticky ref so switching to non-conversation tabs
  (knowledge, tasks, etc.) no longer jumps to the first expert's sessions
- Prevent project switch during active streaming to avoid disrupting AI output
- Keep useMemo pure by extracting ref writes into useEffect
- Remove redundant ternary in openSession
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>