lightwalletd: adaptive reorg-lag tip + non-blocking startup coinsupply

Adaptive-lag: advertise a tip that trails the real tip by a reorg-rate-driven
lag (GetLatestBlock/GetLightdInfo) so wallets anchor shielded spends at a
settled height during reorg churn. Configurable via
-adaptive-lag/-lag-min/-lag-max/-lag-window; monitor_lwd.sh runs
-lag-min 4 -lag-max 12 -lag-window 30.

Startup coinsupply: the informational startup coinsupply RPC (result used only
for a log line) blocked the gRPC bind for minutes on a node whose supply index
is cold, keeping the lite endpoint down on every restart while it also starved
the block-cache ingestor. Run it in a goroutine so the bind is never blocked;
clients still get coinsupply on demand via the GetCoinsupply RPC.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/service.go

@@ -41,9 +41,12 @@ func (s *SqlStreamer) GetCache() *common.BlockCache {
 }
 
 func (s *SqlStreamer) GetLatestBlock(ctx context.Context, placeholder *walletrpc.ChainSpec) (*walletrpc.BlockID, error) {
-	latestBlock := s.cache.GetLatestBlock()
+	// Advertise a tip that trails the real tip by the adaptive confirmation lag,
+	// so wallets anchor shielded spends at a settled height during reorg churn.
+	latestBlock := s.cache.AdvertisedLatestBlock()
 	s.log.WithFields(logrus.Fields{
 		"latestBlock": latestBlock,
+		"adaptiveLag": s.cache.CurrentLag(),
 	}).Info("GetLatestBlock called")
 
 	if latestBlock == -1 {
@@ -321,6 +324,13 @@ func (s *SqlStreamer) GetLightdInfo(ctx context.Context, in *walletrpc.Empty) (*
 		return nil, err
 	}
 
+	// Report the advertised (lag-adjusted) tip so wallets consider themselves
+	// synced at the height they are actually served, not perpetually N behind.
+	advHeight := s.cache.AdvertisedLatestBlock()
+	if advHeight < 0 {
+		advHeight = blockHeight
+	}
+
 	// TODO these are called Error but they aren't at the moment.
 	// A success will return code 0 and message txhash.
 	return &walletrpc.LightdInfo{
@@ -330,7 +340,7 @@ func (s *SqlStreamer) GetLightdInfo(ctx context.Context, in *walletrpc.Empty) (*
 		ChainName:               chainName,
 		SaplingActivationHeight: uint64(saplingHeight),
 		ConsensusBranchId:       consensusBranchId,
-		BlockHeight:             uint64(blockHeight),
+		BlockHeight:             uint64(advHeight),
 		Difficulty:              uint64(difficulty),
 		Longestchain:            uint64(longestchain),
 		Notarized:               uint64(notarized),