fix(lsps4): track channel opens in flight to prevent stuck HTLC loop

When an HTLC arrives for an offline peer, the webhook wakes them up.
On reconnect, peer_connected defers because channels need reestablish.
Once usable, process_pending_htlcs found insufficient capacity but
assumed a channel open was already in flight - with no actual tracking.
Nobody ever opened the channel, causing an infinite retry loop until
the HTLC expired after 45s.

Add channel_opens_in_flight HashSet so process_pending_htlcs can:
- Emit OpenChannel on the first tick when a new channel is needed
- Skip on subsequent ticks while the open is in progress
- Clear the flag on channel_ready or peer_disconnected

Author: martinsaposnic

lightning-liquidity/src/lsps4/service.rs

@@ -101,6 +101,7 @@ where
 	scid_store: ScidStore<L, K>,
 	htlc_store: HTLCStore<L, K>,
 	connected_peers: RwLock<HashSet<PublicKey>>,
+	channel_opens_in_flight: RwLock<HashSet<PublicKey>>,
 	config: LSPS4ServiceConfig,
 }
 
@@ -128,6 +129,7 @@ where
 			config,
 			logger,
 			connected_peers: RwLock::new(HashSet::new()),
+			channel_opens_in_flight: RwLock::new(HashSet::new()),
 		})
 	}
 
@@ -275,6 +277,8 @@ where
 	pub fn channel_ready(
 		&self, counterparty_node_id: &PublicKey,
 	) -> Result<(), APIError> {
+		self.channel_opens_in_flight.write().unwrap().remove(counterparty_node_id);
+
 		let is_connected = self.is_peer_connected(counterparty_node_id);
 
 		log_info!(
@@ -470,6 +474,8 @@ where
 
 	/// Will update the set of connected peers
 	pub fn peer_disconnected(&self, counterparty_node_id: &PublicKey) {
+		self.channel_opens_in_flight.write().unwrap().remove(counterparty_node_id);
+
 		let (was_present, remaining_count) = {
 			let mut peers = self.connected_peers.write().unwrap();
 			let was = peers.remove(counterparty_node_id);
@@ -525,16 +531,23 @@ where
 				);
 				let actions = self.calculate_htlc_actions_for_peer(node_id, htlcs);
 				if actions.new_channel_needed_msat.is_some() {
-					// A channel open is already in flight from htlc_intercepted or
-					// peer_connected. Skip — channel_ready will handle forwarding
-					// once the new channel is established.
+					let already_in_flight = self.channel_opens_in_flight.read().unwrap().contains(&node_id);
+					if already_in_flight {
+						log_info!(
+							self.logger,
+							"[LSPS4] process_pending_htlcs: peer {} needs a new channel, \
+							 skipping (channel open already in flight)",
+							node_id
+						);
+						continue;
+					}
 					log_info!(
 						self.logger,
 						"[LSPS4] process_pending_htlcs: peer {} needs a new channel, \
-						 skipping (channel open already in flight)",
+						 triggering OpenChannel",
 						node_id
 					);
-					continue;
+					self.channel_opens_in_flight.write().unwrap().insert(node_id);
 				}
 				self.execute_htlc_actions(actions, node_id);
 			}