Add stale-job skip check in update_mempool_jobs

[marco-storswift]

Summary

In update_mempool_jobs (main_loop.rs), each update job is processed unconditionally — the code fetches a mutator set update and recomputes the witness even if the mempool entry has already been updated to the latest block tip by another path (e.g., the proof_upgrader loop).

Proposed fix

Before processing a job, check whether the transaction's kernel.mutator_set_hash already matches the tip's mutator set accumulator hash in the mempool. If it does, the job is stale and can be skipped.

The check is:

let gs = global_state_lock.lock_guard().await;
let tip_ms_hash = gs
    .chain
    .light_state()
    .tip()
    .mutator_set_accumulator_after()
    .ok()
    .map(|msa| msa.hash());
if let (Some(current_tx), Some(tip_hash)) =
    (gs.mempool.get(txid), tip_ms_hash)
{
    if current_tx.kernel.mutator_set_hash == tip_hash {
        // skip — already synced
    }
}

Logic explanation

• Acquire a read-only lock (not a write lock, since we are only checking — the write lock is still taken later for the actual update).
• Get the tip block's mutator set accumulator hash from the chain's light state.
• Look up the transaction in the mempool by its txid.
• If both exist and their MS hashes match, the transaction is already at the tip and no update is needed.
• The scoped block ensures the read lock is dropped before the match block, avoiding any deadlock with the later lock_guard_mut() call.

Why this matters

Without this check, the function re-derives the mutator set update and re-witnesses the transaction even when the mempool already has the fresh version. This wastes CPU cycles on redundant computation and delays processing of other update jobs.

[marco-storswift]

When I use the wallet's RPC to generate a transaction, a new block is produced during the process of generating the singleProof. As a result, update_mempool_jobs picks up the old PrimitiveWitness transaction. After my singleProof is generated, when update_mempool_jobs is executed again, it changes the transaction type back to PrimitiveWitness. After that, it never updates again.