Client devs Propose Simplifications to Fast Confirmation Rule

Client devs propose simplifications via new EIPs. Three spec PRs open against the latest spec branch: epochs boundary checkpoint fixing, flexible FCR trigger timing, and using head states for FFG checks. Lodestar's spec tests pass; deploying to staking environments for performance metrics is next. Exchanges get confirmation status from EL 'safe' block tags with no exchange-side code changes needed.