refactor: unify oneLineStr/oneLine into types.OneLine

provider.oneLineStr and gateway.oneLine had byte-identical bodies (flatten
whitespace + cap length). Move the single implementation into the types
package, which both layers already depend on, and delete both locals.

internal/types/types.go

@@ -5,6 +5,7 @@ package types
 import (
 	"encoding/json"
 	"errors"
+	"strings"
 	"time"
 )
 
@@ -159,4 +160,15 @@ type BuildMeta struct {
 	Source    map[string]interface{} `json:"source"`
 }
 
-func Now() int64 { return time.Now().Unix() }
+func Now() int64 { return time.Now().Unix() }
+
+// OneLine flattens an error string to a single line capped at n chars.
+// Shared by the provider layer (upstream error reasons) and the gateway
+// layer (client-facing AUTO-chain summaries).
+func OneLine(s string, n int) string {
+	s = strings.Join(strings.Fields(s), " ")
+	if len(s) > n {
+		s = s[:n] + "..."
+	}
+	return s
+}