feat(routing): add immutable RoutingResult class for routing resolution

packages/core-dart/lib/src/routing/routing_result.dart

@@ -0,0 +1,41 @@
+import 'result.dart';
+
+/// Immutable result object returned from routing resolution.
+///
+/// Holds the [source] tag indicating how the route was resolved,
+/// an optional numeric [id] extracted from the address or memo,
+/// and any [warnings] emitted during resolution.
+final class RoutingResult {
+  final RoutingSource source;
+  final BigInt? id;
+  final List<RoutingWarning> warnings;
+
+  RoutingResult({
+    required this.source,
+    this.id,
+    List<RoutingWarning>? warnings,
+  }) : warnings = List.unmodifiable(warnings ?? const []);
+
+  @override
+  String toString() =>
+      'RoutingResult(source: $source, id: $id, warnings: $warnings)';
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is RoutingResult &&
+          source == other.source &&
+          id == other.id &&
+          _listEquals(warnings, other.warnings);
+
+  @override
+  int get hashCode => Object.hash(source, id, Object.hashAll(warnings));
+
+  static bool _listEquals(List<RoutingWarning> a, List<RoutingWarning> b) {
+    if (a.length != b.length) return false;
+    for (var i = 0; i < a.length; i++) {
+      if (a[i] != b[i]) return false;
+    }
+    return true;
+  }
+}