Preserve text marshalers in absent-facet conversion

Review of the nil fast path identified named nil collections that implement encoding.TextMarshaler rather than json.Marshaler. Keep the parent representation for both interfaces and retain matching byte-level controls.

Contract-Neutral: Conversion work only; retain the exact existing JSON and text-marshaler representations and all broadcast fields and freshness boundaries.
Change-source: pulse-maintainer

internal/monitoring/broadcast_conversion_test.go

@@ -22,6 +22,14 @@ type projectionNilMap map[string]string
 
 func (projectionNilMap) MarshalJSON() ([]byte, error) { return []byte(`{"custom":true}`), nil }
 
+type projectionNilTextSlice []string
+
+func (projectionNilTextSlice) MarshalText() ([]byte, error) { return []byte("custom-text"), nil }
+
+type projectionNilTextMap map[string]string
+
+func (projectionNilTextMap) MarshalText() ([]byte, error) { return []byte("custom-text"), nil }
+
 type projectionInvalidJSON struct{}
 
 func (projectionInvalidJSON) MarshalJSON() ([]byte, error) { return []byte(`{broken`), nil }
@@ -53,6 +61,8 @@ func TestBroadcastRawJSONPreservesAbsentEmptyAndFailureSemantics(t *testing.T) {
 		{"empty-slice", []string{}}, {"empty-map", map[string]string{}},
 		{"named-nil-slice-marshaler", projectionNilSlice(nil)},
 		{"named-nil-map-marshaler", projectionNilMap(nil)},
+		{"named-nil-slice-text-marshaler", projectionNilTextSlice(nil)},
+		{"named-nil-map-text-marshaler", projectionNilTextMap(nil)},
 		{"nil-pointer-marshaler", (*projectionNilSlice)(nil)},
 		{"invalid-json", projectionInvalidJSON{}}, {"encode-failure", projectionFailedJSON{}},
 		{"invalid-float", math.NaN()}, {"raw-null", json.RawMessage(`null`)},

internal/monitoring/monitor.go

@@ -3,6 +3,7 @@ package monitoring
 import (
 	"context"
 	"crypto/sha256"
+	"encoding"
 	"encoding/hex"
 	"encoding/json"
 	stderrors "errors"
@@ -6654,7 +6655,9 @@ func monitorRawJSON(value interface{}) json.RawMessage {
 	case reflect.Slice, reflect.Map:
 		if v.IsNil() {
 			if _, custom := value.(json.Marshaler); !custom {
-				return nil
+				if _, customText := value.(encoding.TextMarshaler); !customText {
+					return nil
+				}
 			}
 		}
 	}