- Add cover traffic support with constant rate as per spec
- Add mix-user-message-limit and mix-disable-spam-protection CLI flags
- Fix option_shims.nim double-evaluation bug causing UnpackDefect crash
in ping (template expanded await expression twice, racing two calls)
- Reduce default rate limit to 2 msgs/epoch for simulation testing
- Add check_cover_traffic.sh metrics monitoring script
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>