fix(cbf): advance sync timestamps and handle unknown block on resume

Fixes a hang in start/stop/reinit after a checkpoint-based resume where
`wait_for_cbf_sync` timed out because neither sync timestamp advanced.

- `sync_lightning_wallet`: when no scripts are registered, still call
`update_node_metrics_timestamp` so callers waiting on a strict advance
of `latest_lightning_wallet_sync_timestamp` make progress. The
empty-scripts and normal paths now share a single timestamp-update
site at the end of the closure.
- `fee_rate_cache_from_cbf`: treat `FetchBlockError::UnknownHash` as a
skip-this-cycle condition instead of an error. After a checkpoint
resume, `requester.chain_tip()` can return the checkpoint hash which
has no `BlockNode` in kyoto's tree yet, previously surfacing as
`FeerateEstimationUpdateFailed` from `node.start()`.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: randomlogin

src/chain/cbf.rs

@@ -14,6 +14,7 @@ use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 use bdk_chain::{BlockId, ConfirmationBlockTime, TxUpdate};
 use bdk_wallet::Update;
 use bip157::chain::{BlockHeaderChanges, ChainState};
+use bip157::error::FetchBlockError;
 use bip157::{
 	BlockHash, Builder, Client, Event, HeaderCheckpoint, Info, Node as CbfNode, Requester,
 	SyncUpdate, TrustedPeer, Warning,
@@ -729,35 +730,34 @@ impl CbfChainSource {
 			let scripts: Vec<ScriptBuf> = self.registered_scripts.lock().unwrap().clone();
 			if scripts.is_empty() {
 				log_debug!(self.logger, "No registered scripts for CBF lightning sync.");
-				return Ok(());
-			}
-
-			let timeout_fut = tokio::time::timeout(
-				Duration::from_secs(
-					self.sync_config.timeouts_config.lightning_wallet_sync_timeout_secs,
-				),
-				self.sync_lightning_wallet_op(
-					requester,
-					channel_manager,
-					chain_monitor,
-					output_sweeper,
-					scripts,
-				),
-			);
+			} else {
+				let timeout_fut = tokio::time::timeout(
+					Duration::from_secs(
+						self.sync_config.timeouts_config.lightning_wallet_sync_timeout_secs,
+					),
+					self.sync_lightning_wallet_op(
+						requester,
+						channel_manager,
+						chain_monitor,
+						output_sweeper,
+						scripts,
+					),
+				);
 
-			match timeout_fut.await {
-				Ok(res) => res?,
-				Err(e) => {
-					log_error!(self.logger, "Sync of Lightning wallet timed out: {}", e);
-					return Err(Error::TxSyncTimeout);
-				},
-			};
+				match timeout_fut.await {
+					Ok(res) => res?,
+					Err(e) => {
+						log_error!(self.logger, "Sync of Lightning wallet timed out: {}", e);
+						return Err(Error::TxSyncTimeout);
+					},
+				};
 
-			log_debug!(
-				self.logger,
-				"Sync of Lightning wallet via CBF finished in {}ms.",
-				now.elapsed().as_millis()
-			);
+				log_debug!(
+					self.logger,
+					"Sync of Lightning wallet via CBF finished in {}ms.",
+					now.elapsed().as_millis()
+				);
+			}
 
 			update_node_metrics_timestamp(
 				&self.node_metrics,
@@ -915,6 +915,18 @@ impl CbfChainSource {
 					.await
 				{
 					Ok(Ok(indexed_block)) => indexed_block,
+					Ok(Err(FetchBlockError::UnknownHash)) => {
+						// Kyoto doesn't know this block yet (e.g. startup before
+						// filter sync, or hash is at/below the resume checkpoint).
+						// Skip this cycle and try again later.
+						log_debug!(
+							self.logger,
+							"CBF node does not yet have block {} for fee estimation; \
+							 skipping until sync progresses.",
+							current_hash,
+						);
+						return Ok(None);
+					},
 					Ok(Err(e)) => {
 						log_error!(
 							self.logger,