chanmon_consistency: resolve timelocked HTLCs during settlement

When channels have been force-closed, the 0xff settlement needs to
advance chain height past HTLC cltv_expiry timelocks so that the
OnchainTxHandler releases timelocked HTLC-timeout claim packages for
broadcast. Without this, HTLC-timeout transactions would never be
generated and in-flight HTLCs would remain unresolved.

The settlement advances in two phases of 250 blocks each:
1. Past cltv_expiry: triggers HTLC-timeout tx broadcasts, which the
   existing drain-and-confirm loop picks up and confirms on-chain.
2. Past the CSV delay (BREAKDOWN_TIMEOUT=144): allows SpendableOutputs
   events to fire for both the to_local output and resolved HTLC
   outputs.

Each phase syncs all nodes to the new chain tip and runs
process_all_events\!() to drain all resulting messages, events,
broadcasts, and monitor updates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: joostjager

fuzz/src/chanmon_consistency.rs

@@ -2890,6 +2890,61 @@ pub fn do_test<Out: Output + MaybeSend + MaybeSync>(
 				}
 				process_all_events!();
 
+				// If any channels were force-closed, advance chain height past HTLC
+				// timelocks so HTLC-timeout transactions can be broadcast, confirmed,
+				// and fully resolved. We advance in two phases:
+				// 1) Past cltv_expiry so HTLC-timeout txs are released
+				// 2) Past the CSV delay so SpendableOutputs events fire
+				if !closed_channels.borrow().is_empty() {
+					chain_state.advance_height(250);
+					sync_with_chain_state(
+						&chain_state,
+						&nodes[0],
+						&monitor_a,
+						&mut node_height_a,
+						None,
+					);
+					sync_with_chain_state(
+						&chain_state,
+						&nodes[1],
+						&monitor_b,
+						&mut node_height_b,
+						None,
+					);
+					sync_with_chain_state(
+						&chain_state,
+						&nodes[2],
+						&monitor_c,
+						&mut node_height_c,
+						None,
+					);
+					process_all_events!();
+
+					chain_state.advance_height(250);
+					sync_with_chain_state(
+						&chain_state,
+						&nodes[0],
+						&monitor_a,
+						&mut node_height_a,
+						None,
+					);
+					sync_with_chain_state(
+						&chain_state,
+						&nodes[1],
+						&monitor_b,
+						&mut node_height_b,
+						None,
+					);
+					sync_with_chain_state(
+						&chain_state,
+						&nodes[2],
+						&monitor_c,
+						&mut node_height_c,
+						None,
+					);
+					process_all_events!();
+				}
+
 				// Verify no payments are stuck - all should have resolved
 				for (idx, pending) in pending_payments.borrow().iter().enumerate() {
 					assert!(