Improve D&D registry normalization efficiency

internal/modules/dnd/normalize/locationregistry/normalizer_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"reflect"
+	"strconv"
 	"strings"
 	"testing"
 
@@ -60,6 +61,23 @@ func TestNormalizePreparesOnlyExactDuplicatesAndRetainsSameNameAndNestedPlaces(t
 	}
 }
 
+func BenchmarkExactDuplicateGroupsManyDistinct(b *testing.B) {
+	records := make([]normalizedRecord, 1_000)
+	for index := range records {
+		records[index] = normalizedRecord{location: dnd.Location{
+			Name:       "Location " + strconv.Itoa(index),
+			SourceRefs: []source.SourceRef{{SourceID: "session", StartUnitID: index + 1, EndUnitID: index + 1}},
+		}}
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+	for iteration := 0; iteration < b.N; iteration++ {
+		if groups := exactDuplicateGroups(records); len(groups) != len(records) {
+			b.Fatalf("group count = %d, want %d", len(groups), len(records))
+		}
+	}
+}
+
 func TestNormalizeAppliesSafeAliasGroupAndUsesContextualInputs(t *testing.T) {
 	client := &recordingLocationNormalizerClient{response: `{"duplicate_groups":[{"members":["candidate-000001","candidate-000002"],"canonical":"candidate-000002"}]}`}
 	doc := semanticDocument()