EIP-7917: Deterministic proposer lookahead

EIP-7917 proposes storing the proposer schedule for upcoming epochs in the beacon root at the start of each epoch, so the lookahead is deterministic. According to the summary, this removes unpredictable changes to the next epoch's lookahead caused by effective balance fluctuations, such as slashings, penalties, or increased validator balances, an issue made worse by EIP-7251's MaxEB increase. The text says this would let preconfirmation protocols rely on a stable schedule with less complexity, and give straightforward on-chain access to the lookahead via the beacon root. It also says the change removes a potential source of grinding attacks via effective balance changes. The update log shows the EIP was scheduled for Fusaka with a target of fusaka-devnet-1 as of 2025-05-29.