feat(hot)!: add table for journal hashes

[Fraser999]

Summary

Adds a JournalHashes<BlockNumber => B256> hot table so nodes can re-seed the rolling previous-journal hash across restarts and reorgs (ENG-2017). Hot-only, opt-in per block.

Changes

• New table JournalHashes<BlockNumber => B256> plus HotDbRead::get_journal_hash and UnsafeDbWrite::put_journal_hash.
• ExecutedBlock.journal_hash: Option<B256> + builder setter. UnifiedStorage::append_blocks persists it in the same hot transaction as headers/bundle.
• HistoryWrite::unwind_above deletes journal hashes alongside change-sets/headers, independent of last_block_number().
• New STANDARD_TABLES const in signet-hot as the single source of truth for table creation and MDBX FSI cache seeding. queue_db_init and read_known_fsi both iterate it.
• Fix: unwind_above(u64::MAX) now short-circuits via checked_add instead of overflowing block + 1 (wraps to 0 in release, panics in debug).
• From<ExecutedBlock> for BlockData destructures explicitly so new fields trip a compile error on the cold side.

API breakages

• ExecutedBlock::new() removed - use ExecutedBlockBuilder instead.
• ExecutedBlock gains a new public journal_hash field. Struct-literal construction (ExecutedBlock { header, .. }) and exhaustive destructuring without .. will no longer compile.

Test plan

• cargo t -p signet-hot -p signet-hot-mdbx -p signet-storage --all-features
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo clippy --workspace --all-targets --no-default-features -- -D warnings
• cargo +nightly fmt -- --check
• New tests: test_journal_hash_roundtrip (conformance), append_blocks_persists_journal_hashes / unwind_above_drops_journal_hashes (integration), unwind_above_u64_max_is_noop / unwind_above_below_u64_max_deletes_max_entry (overflow boundary). test_unwind_conformance updated to cover JournalHashes.

Notes

• put_journal_hash has no consistent-trait wrapper; callers are responsible for pairing writes with a header. unwind_above cleans both regardless.
• replay_to_cold silently discards journal_hash (hot-only).

---

PR description drafted by Claude (Opus 4.7, 1M context) via Claude Code.

[Fraser999]

• feat(hot)!: add table for journal hashes #70 👈 (View in Graphite)
• main

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[prestwich]

main thing i think is

[prestwich]

nit: usually with_journal_hash or some other verb that indicates mutating

[Fraser999]

I prefer the with_ prefix too, but all other setters don't have it.

I'd be OK with adding it to all of them. It'd be a breaking change to the API, but this PR already has other breaking changes, so now might be a good time to make that change if we want it?

[prestwich]

let's go ahead and make the change :)

[Fraser999]

Done in 5d967f0.

[prestwich]

I don't mind this complexity addition

[prestwich]

[Claude Code]

Approved. Reviewed for correctness and CLAUDE.md compliance — no bugs found and no convention violations.

Verified sound:

• `unwind_above` `checked_add(1)` overflow guard and the `JournalHashes` range-delete ordering.
• `queue_raw_create` flag refactor via `from_create_args`/`is_dupsort`/`is_dup_fixed` is equivalent to the prior inline behavior.
• `append_blocks` persists journal hashes atomically in the same writer/transaction as headers/bundle.
• `NUM_TABLES` (now `STANDARD_TABLES.len()`) — all consumers derive from the const, no drift.

One optional follow-up, not blocking: the agreed-upon `with_` prefix rename on the `ExecutedBlockBuilder` setters wasn't applied. Fraser can update the naming before merging if he wants.

Minor: the PR description still mentions the pre-upgrade FSI fallback and `open_tolerates_pre_upgrade_db` test that were removed in `ae5e263`; worth tidying the description before merge.