Lodestar Clears Key Hurdles in Spec Tests and Readies Staking Deployment

Here is a 60-word summary of the content: Lodestar's spec tests are passing and it will deploy to staking environments. Three PRs opened reduce implementation complexity: fixing epoch boundary checkpoints (#25), flexible FCR trigger timing (#26), and using head state for FFG check (#27). Feedback on these changes is welcome, particularly from client teams that are still updating their implementations.