Mid-Flight Rescue — γ → in-flight α/β re-pinning channel

Mid-flight γ→in-flight-α rescue channel. Use when γ needs to change a load-bearing fact (pinned axis, scope, AC, blocker) after α has begun coding, when γ edits the cycle's GitHub issue body mid-cycle, or when a spec change lands on origin/main while α/β polling sessions are in-flight.