feat: FCU unwind: properly reorg in-memory canonical state and update latest block

[pycckuu]

Fix FCU when new head is an ancestor (unwind). Previously we only updated the header, leaving in-memory canonical state stale, causing tx validation issues (e.g., "nonce too low"). Now we detect unwind, reorg in-memory state (remove old blocks, load ancestor), and keep TreeState and CanonicalInMemoryState in sync.

Code Changes

• tree/mod.rs:
• Add: log_chain_update_type, handle_chain_unwind, collect_blocks_for_removal, apply_canonical_ancestor_via_reorg, handle_chain_advance_or_same_height, ensure_block_in_memory.
• Replace header-only update with:

  self.log_chain_update_type(...);
  self.state.tree_state.set_canonical_head(canonical_header.num_hash());
  if new_head_number < current_head_number {
      self.handle_chain_unwind(current_head_number, canonical_header)
  } else {
      self.handle_chain_advance_or_same_height(canonical_header)
  }

• Reorg on unwind:

  self.canonical_in_memory_state.update_chain(NewCanonicalChain::Reorg { new, old });
  self.canonical_in_memory_state.set_canonical_head(canonical_header.clone());

• Advance/same-height: ensure block committed into memory if missing.
• Interim method update_latest_block_to_canonical_ancestor added, then superseded by full unwind handling.
• tree/tests.rs:
• New test test_fcu_with_canonical_ancestor_updates_latest_block asserting both TreeState and in-memory head match the ancestor after FCU.

Reason for Changes

Correctness: prevent stale in-memory state on reorgs that led to txpool/state provider errors.

Impact of Changes

• Correct state after unwinds; eliminate nonce/state desync errors.
• Low overhead; clearer logging.

Test Plan

• Run: cargo test -p engine_tree test_fcu_with_canonical_ancestor_updates_latest_block.

How the reviewer should test the fix

• Unwind: head=4 → FCU to 2; verify removal of [3,4] and head=2 in both states.
• Advance: head=2 → FCU to 3; verify block 3 committed and head updated.
• Check logs for correct classification.

Other useful info

If ancestor block missing from storage, we warn and still update header to avoid desync.

Closes #17798

[pycckuu]

@mattsse I've rebased on the latest main branch changes. Could you please review? I'd recommend checking by commit since one commit addresses linting issues with cargo +nightly fmt and touches many files.

[mediocregopher]

Hi @pycckuu, can you leave out the linting changes which aren't related to the fix being submitted? They make it impossible to review this.

[pycckuu]

Hi @pycckuu, can you leave out the linting changes which aren't related to the fix being submitted? They make it impossible to review this.

I can definitely do that, but as mentioned earlier, reviewing commit-by-commit would be much more manageable. I'm also unsure how to handle linting issues that originate from the main branch and code I haven't modified.

[pycckuu]

@mediocregopher I've removed the styling commit. Could you please review it? Thanks in advance.

[mediocregopher]

One nit and one question, will want @mattsse to look at it as well

[mediocregopher]

Is it correct that this is being called after the process_payload_attributes if-branch? If attrs.is_some() then this line never gets hit.

[pycckuu]

I suppose, the assumption here is:

• Without attrs: We're just updating the head, so the state needs to be fixed
• With attrs: We're building the payload and assuming the state is already correct

The placement of the new code was suggested by @mattsse in 9e8735d

[mediocregopher]

lgtm, pending matt's review

[pycckuu]

gentle ping @mattsse!

[mattsse]

I'm okay with this because this code path is only reachable if explicitly opt-in.