Unresolved TODOs from PR #4828

We merged in #4828 and decided to work on the unresolved items iteratively.

Here are the review threads that I think we did not reach a conclusion on:

## Prover Registration and Whitelist Mechanism

See review thread [here](https://github.com/ethereum/consensus-specs/pull/4828#discussion_r2717344753)

There was a conversation around what the whitelist should be and the mechanism for registering and updating provers.

- Suggestion to use a BPO-like (Prover Parameter Only) config loaded as node configuration
- Main concern for this mechanism was around DoS if `execution_proof` topic is spammed with invalid proofs
- Reference doc: https://hackmd.io/@kevaundray/SJjGnqz8bl

## Stateless validation mode

See review thread [here](https://github.com/ethereum/consensus-specs/pull/4828#discussion_r2718892537)

Discussion around whether the specs should support running without an EL

- Original purpose of optional proofs was to be able to run without an EL. However, we may want to allow both ExecutionEngine and ProofEngine

## Reuse ExecutionPayloadHeader

@jihoonsong notes [here](https://github.com/ethereum/consensus-specs/pull/4828/changes#r2720997731) that ExecutionPayloadHeader is constructed twice with the same fields and could be reused from the `verify_new_payload_request_header` call

## proof_gen_id vs proof_type Naming

See review thread [here](https://github.com/ethereum/consensus-specs/pull/4828#discussion_r2721129213)

- Clarification needed on what "proof instance" means

## Async Proof delivery and failure handling

See review thread [here](https://github.com/ethereum/consensus-specs/pull/4828#discussion_r2721174717)

- Suggestion to add a note about fallback behavior

## Fork Choice and Proof Verification Timing

See review thread [here](https://github.com/ethereum/consensus-specs/pull/4828#discussion_r2721258777)

Discussion about when verify_new_payload_request_header runs.

## K-out-of-N Policy Documentation

@jihoonsong noted that the k-out-of-n proof policy should be described somewhere in the spec.