Enable Cortex hooks and run Phase 4 A/B sessions

[Jmeg8r]

Enable Cortex session hooks (transcript parsing, briefing generation) and conduct a comparable set of development sessions to measure the impact of event-sourced memory on session continuity.

Acceptance Criteria

• Cortex hooks enabled and verified working
• Equivalent number of sessions run with Cortex active
• Same metrics captured as baseline for direct comparison
• Session transcripts and Cortex-generated briefings saved