Exclude slashed validators from all duties (EIP-8045)

[barnabasbusa]

Summary

Implements EIP-8045 ("Exclude slashed validators from all duties") at the Gloas fork. Paired with the EIP text update in ethereum/EIPs#11443.

Spec changes (specs/gloas/beacon-chain.md)

• Modified get_beacon_proposer_indices — filter slashed validators out of the active set upfront, before invoking compute_proposer_indices. The EIP-7917 proposer_lookahead is populated from this function each epoch, so it is guaranteed to contain only active and unslashed validators.
• Modified compute_balance_weighted_selection — in-loop slashed skip after the candidate is drawn. Because Gloas routes sync committee selection, proposer selection, and PTC selection (get_next_sync_committee_indices, compute_proposer_indices, compute_ptc) through this helper, a single change covers every balance-weighted duty, including any future one built on the same primitive.

The two layers intentionally use different filtering strategies, consistent with the EIP's rationale: upfront for proposer (small candidate set, avoids wasted shuffling work), in-loop for the helper (matches its existing iterative acceptance-check shape).

Intro bullet list updated to reference EIP-8045 alongside EIP-7732. No new state fields, no fork transition logic, so specs/gloas/fork.md is untouched.

Scope note

EIP-8045 targets balance-weighted duty selection. Attestation beacon committees (compute_committee) are not modified — they're shuffle-based, not balance-weighted, and slashed attestors are already rejected at process_attestation time. See the EIP text for the full rationale.

Design notes

• proposer_lookahead is pre-computed once per epoch by process_proposer_lookahead. A validator slashed inside an already-populated lookahead window is not retroactively removed — the EIP security considerations explicitly accept this, since with EIP-7917 the lookahead is state-resident and slashings no longer reshuffle it.
• With the proposer-level upfront filter in place, the compute_balance_weighted_selection slashed skip is a defense-in-depth no-op for the proposer path, but load-bearing for sync committee and PTC.
• No get_next_sync_committee_indices override needed in this PR — the Gloas version already calls compute_balance_weighted_selection, and the updated EIP text (Update EIP-8045: Exclude slashed validators from all duties EIPs#11443) was trimmed accordingly.

Tests

All six EIP test cases (plus PTC coverage) are included under tests/core/pyspec/eth_consensus_specs/test/gloas/:

• Slashed validators absent from newly-appended entries of state.proposer_lookahead after process_proposer_lookahead
• Full SLOTS_PER_EPOCH lookahead entries still produced with many slashed validators
• Slashed validators absent from get_next_sync_committee_indices output
• Full SYNC_COMMITTEE_SIZE committee produced with many slashed validators
• compute_balance_weighted_selection skips slashed (shuffled path)
• compute_balance_weighted_selection skips slashed (in-order path, PTC code path)
• compute_ptc excludes slashed validators from every slot's PTC
• Existing EIP-7917 invariant (slashing inside the filled lookahead window does not mutate preserved entries) — already covered by test/fulu/epoch_processing/test_process_proposer_lookahead.py

Local verification: make lint clean, all 7 new tests pass on the minimal preset.

Test plan

• CI passes on all presets
• Cross-client review of slashed-skip behavior in mass-slashing regimes

Related

• EIP text update: Update EIP-8045: Exclude slashed validators from all duties EIPs#11443
• Depends on EIP-7917 (proposer_lookahead, already in Fulu) and EIP-7732 (compute_balance_weighted_selection, Gloas)