fix(bridge): correct error wrapping, trace_id key, and a log message (#1095)

Three diagnostics/observability fixes (no behavior change to fund flow):

1. bridge.go: the tfchain and stellar subscription error branches checked
   `data.Err != nil` but wrapped the stale outer-scope `err`, so a real
   subscription failure was reported with the wrong/empty cause. Wrap
   `data.Err` in both arms.

2. stellar.go: the `stellar_transaction_submitted` success log read the
   trace id with the string key `ctx.Value("trace_id")`, but the value is
   stored under the typed key `TraceIdKey{}`, so trace_id was always
   logged as <nil>. Use `TraceIdKey{}`.

3. client.go: RetrySetWithdrawExecuted (which calls
   SetBurnTransactionExecuted) logged "setting refund transaction as
   executed". Corrected to "burn transaction".

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: sameh-farouk

bridge/tfchain_bridge/pkg/bridge/bridge.go

@@ -146,7 +146,7 @@ func (bridge *Bridge) Start(ctx context.Context) error {
 		select {
 		case data := <-tfchainSub:
 			if data.Err != nil {
-				return errors.Wrap(err, "failed to get tfchain events")
+				return errors.Wrap(data.Err, "failed to get tfchain events")
 			}
 			for _, withdrawCreatedEvent := range data.Events.WithdrawCreatedEvents {
 				err := bridge.handleWithdrawCreated(ctx, withdrawCreatedEvent)
@@ -190,7 +190,7 @@ func (bridge *Bridge) Start(ctx context.Context) error {
 			}
 		case data := <-stellarSub:
 			if data.Err != nil {
-				return errors.Wrap(err, "failed to get stellar payments")
+				return errors.Wrap(data.Err, "failed to get stellar payments")
 			}
 
 			for _, mEvent := range data.Events {

bridge/tfchain_bridge/pkg/stellar/stellar.go

@@ -368,7 +368,7 @@ func (w *StellarWallet) submitTransaction(ctx context.Context, txn *txnbuild.Tra
 		return errors.Wrap(err, "an error occurred while submitting the transaction")
 	}
 	log.Info().
-		Str("trace_id", fmt.Sprint(ctx.Value("trace_id"))).
+		Str("trace_id", fmt.Sprint(ctx.Value(TraceIdKey{}))).
 		Str("event_action", "stellar_transaction_submitted").
 		Str("event_kind", "event").
 		Str("category", "vault").

bridge/tfchain_bridge/pkg/substrate/client.go

@@ -63,7 +63,7 @@ func NewSubstrateClient(url string, seed string) (*SubstrateClient, error) {
 func (s *SubstrateClient) RetrySetWithdrawExecuted(ctx context.Context, tixd uint64) error {
 	err := s.SetBurnTransactionExecuted(s.identity, tixd)
 	for err != nil {
-		log.Err(err).Msg("error while setting refund transaction as executed")
+		log.Err(err).Msg("error while setting burn transaction as executed")
 
 		select {
 		case <-ctx.Done():