feat(state): persist confirmed header root prefixes

[p0mvn]

Summary

• Accept confirmed-prefix tree-aux roots for Zakura header range commits.
• Add read support for reconstructing the confirmed header history-tree frontier from durable roots.

Test plan

• cargo fmt --all -- --check
• cargo test -p zebra-state best_header_history_tree

Stack

Depends on the chain helper PR.

AI disclosure

Used Cursor to split PR #458 into stacked branches and prepare this PR.

[v12-auditor]

Note

Complete: Audit complete. V12 found one issue worth reviewing.

Open the full results here.

Finding	Severity	Details
F-96421	🟠 High	Valid Header Roots Rejected The state commit API now documents and enforces a tree_aux_roots shape that is incompatible with the live Zakura header-sync protocol. Request::CommitHeaderRange says forward ranges should carry a confirmed prefix one shorter than headers, and prepare_header_range_batch_with_roots rejects every non-empty vector unless tree_aux_roots.len() + 1 == headers.len(). The network layer still defines Headers.tree_aux_roots as parallel to headers, encoding and validation require the root count to equal the header count, and the receiving reactor dispatches that full-length vector unchanged. The zebrad driver forwards the vector unchanged into zebra_state::Request::CommitHeaderRange, so any protocol-valid rooted response deterministically fails with TreeAuxRootCountMismatch. The driver then classifies that error as an invalid peer range, so the node treats a compliant peer response as misbehavior instead of committing the header range.

Analyzed five files, diff 23a8175...d3ddb6f.