perf: remove redundant ancestry submission work

[0xalpharush]

Summary

Follow-up to #689 that removes redundant ancestry-submission work:

• keep cache hits read-only, fetch misses concurrently, and resolve them by index
• release cached ancestry headers and backing allocation once recovery returns to direct mode
• extract pure ancestry resolution with property tests for ordering, cache partitions, malformed sets, and parent links
• avoid payload formatting, duplicate logs/RPCs, and the stale zone-l1 -> lru lockfile edge

Why

The removed ZonePortal.blockHash read only warned and submitted anyway. The monitor already preflights the same invariant and resyncs, while the contract rejects a mismatch on-chain, so removing it does not change correctness or the existing TOCTOU race.

Validation

• cargo test -p zone-sequencer --lib — 54 passed
• five resolver properties, 128 generated cases each
• cargo clippy -p zone-sequencer --lib --tests -- -D warnings
• cargo fmt --all -- --check
• independent Codex review — no remaining findings

The ignored full-gap E2E passed in 330.97s and remains too slow for per-PR CI.