Branch Tracking Analytics

What: New telemetry event to track forked conversation branches in chat history.

Details:

• Event tengu_session_forked_branches_fetched tracks branch statistics
• Metrics: total sessions, sessions with branches, max branches per session, average branches
• Only fires when at least one session has multiple branches (max > 1)
• Helps understand user exploration patterns
• Evidence: Function f1I() at line 474125 in pretty-v2.0.34.js