enhancement: checkpoint logic doesn't account for chain finality

[user1303836]

Summary

In `adapters/src/repo.rs:42-78`, `build_checkpoint()` stores the latest slot/block/timestamp without applying chain-specific finality delays. Different chains have different finality semantics:

• Solana: Probabilistic finality (can reorg within ~32 slots)
• EVM: Probabilistic block finality (~15 blocks on mainnet)
• Hyperliquid: Instant finality

Impact

• On chain reorg, the checkpoint may point past the reorg depth
• Transactions could be skipped or duplicated on restart after a reorg
• Different chains have silently different reliability guarantees

Recommended Fix

Apply a finality buffer per network before storing checkpoints:

let safe_slot = match finality_model {
    ProbabilisticSlot => latest_slot.saturating_sub(32),
    ProbabilisticBlock => latest_block.saturating_sub(15),
    DeterministicBlock => latest_block.saturating_sub(1),
    Instant => latest_value,
};

🤖 Generated with Claude Code