Clear() moved before the announced-while-reconciling filter in HandleSketchExtension, emptying the filter set

This description is AI generated, mistakes can be made.

Intent: Clear() calls ClearLocalSetSnapshot(), which empties m_announced_while_reconciling, so the filter becomes a no-op and we re-announce to the peer txs it sent us during the round. This is medium rather than low because a peer can inflate our INV/tx traffic on every extension round.

Behaviour change: Original: after an extension round, txs the peer relayed to us mid-round are not announced back. Mutant: they are included in txs_to_announce and INVed to the peer that already gave them to us.

Trigger: Initiator side, extension round: after we snapshot at the failed initial sketch, the peer sends a TX/INV for a wtxid in our snapshot (TryRemovingFromSet / RemoveFromSets flags it in m_announced_while_reconciling). The peer then sends the extension SKETCH, which either decodes with that tx in the diff or fails (announce all of the snapshot).

Spec violation: Documented invariant in the file: 'Filter out transactions received from the peer while reconciling.'

Severity if undetected: medium

Why tests miss it: txreconciliation_tests.cpp (no initiator extension test; the RemoveFromSetsTest filter check is on the responder HandleReconcilDiff path), p2p_txrecon_initiator.py interleaved test covers only INIT_REQUESTED, not extension

Plausibility: Putting the 'update state' step next to the result computation and filtering last looks like harmless tidying. It is not obvious that Clear() wipes the filter set.

Equivalence risk: Equivalent only when m_announced_while_reconciling is empty, i.e. the peer sent nothing mid-round.