docs: add gt nudge guidance to mayor template (hq-6h9w4o)

- Add Coordination section with gt nudge command
- Clarify line 180: routine nudging is Witness job, Mayor can nudge stuck refinery/witness
- Add warning to NEVER use tmux send-keys (drops Enter key)
- Includes liftoff test timestamp in manager.go

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/polecat/manager.go

@@ -1,3 +1,5 @@
+// Liftoff test: 2026-01-09T14:30:00
+
 package polecat
 
 import (