fix(storage): store fork-choice votes independently

[dicethedev]

🗒️ Description / Motivation

This PR fixes fork-choice vote tracking so validator votes are stored independently from aggregated proofs and gossip signatures.

Previously, fork-choice votes were derived from bounded in-memory proof/signature buffers. When those buffers evicted old entries through FIFO cleanup, a validator’s latest vote could disappear even though the vote should still count for fork choice. This PR adds a separate proof-less vote store so fork-choice weights are not affected by proof/signature retention.

What Changed

• Updated crates/storage/src/store.rs

  • Added an independent latest-vote store keyed by validator index.
  • Records known fork-choice votes when aggregated payloads become known.
  • Records block-included attestation votes separately from proof storage.
  • Keeps proof buffers for aggregation/proposal behavior only.
  • Prunes stored votes once their target is finalized.

• Updated crates/blockchain/src/store.rs

  • Inserts block-included attestation votes into the independent vote store during block processing.

Correctness / Behavior Guarantees

• Fork-choice votes no longer disappear when proof or signature buffers evict entries.
• Existing proof/signature buffer behavior is preserved for aggregation and block proposal.
• Latest-vote selection keeps the existing rule: higher slot wins, and same-slot ties use the canonical attestation-data root.
• Finalized-target votes are pruned once they can no longer affect fork choice.

Tests Added / Run

• Added regression coverage for votes surviving aggregated proof FIFO eviction.
• Added coverage for pruning finalized-target votes from the independent vote store.

Related Issues / PRs

• Closes Store fork-choice votes independently from proofs and signatures #504

✅ Verification Checklist

• Ran make fmt — clean
• Ran make lint (clippy with -D warnings) — clean
• Ran make test (cargo test --workspace --profile release-fast) — all passing

[greptile-apps]

Greptile Summary

This PR separates latest fork-choice votes from bounded proof retention.

• Adds a per-validator in-memory latest-vote store and deterministic replacement rule.
• Records votes from known aggregates, promoted aggregates, and block-included attestations.
• Prunes votes when finalization advances and adds FIFO-eviction and pruning tests.
• Updates block processing to record included attestation votes independently of proofs.

Confidence Score: 4/5

This PR should not merge until vote pruning preserves latest messages whose heads remain relevant above the finalized checkpoint.

The new pruning predicate uses the attestation target, while LMD-GHOST consumes its head; after finalization this can remove live-branch voting weight from subsequent head calculations.

Files Needing Attention: crates/storage/src/store.rs

Important Files Changed

Filename	Overview
crates/storage/src/store.rs	Adds the independent latest-vote store and ingestion paths, but pruning by target slot can remove votes whose heads remain relevant to fork choice.
crates/blockchain/src/store.rs	Records validated block-included attestation votes after persisting the imported block and state.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[Known aggregate] --> V[Independent latest-vote store]
  B[Block-included attestation] --> V
  A --> P[Bounded proof buffer]
  V --> F[LMD-GHOST fork choice]
  C[Finalization advances] --> R[Prune votes by target slot]
  R --> V

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Prompt To Fix All With AI

### Issue 1
crates/storage/src/store.rs:1087-1090
**Target-based pruning drops live votes**

When a validator's latest attestation targets a finalized checkpoint but its head remains on a live post-finalization branch, `prune_known_votes` removes the vote based solely on `target.slot`. LMD-GHOST weights `head.root`, so subsequent head calculations lose that validator's weight and can select the wrong branch until a replacement vote arrives.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "fix(storage): store fork-choice votes in..." | Re-trigger Greptile}

[MegaRedHand]

Looks good

Left some comments about pruning. The issue didn't mention it, but the main issue with how we stored votes is that proof are pruned regularly, which shouldn't affect votes: LMD-GHOST uses the latest message from each validator, so otherwise no pruning should happen.

Also, an additional PR is needed to finish addressing the issue, since we still need to replace the payloads and proofs in fork-choice with the new votes.

[MegaRedHand]

There are some conflicts

[dicethedev]

There are some conflicts

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