fix(core): Force-set replayId on frozen baggage for buffer mode errors

Replace the TraceContext.withReplayId approach with
Baggage.forceSetReplayId — the DSC that relay reads comes from
the transaction's baggage, not the envelope header trace context.
After captureReplay() sets the replayId on scope, force-set it on
the transaction's frozen baggage so the envelope header carries
the correct replay_id in the DSC.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: romtsn

sentry/api/sentry.api

@@ -37,6 +37,7 @@ public final class io/sentry/Baggage {
 	public fun <init> (Lio/sentry/Baggage;)V
 	public fun <init> (Lio/sentry/ILogger;)V
 	public fun <init> (Ljava/util/concurrent/ConcurrentHashMap;Ljava/lang/Double;Ljava/lang/Double;Ljava/lang/String;ZZLio/sentry/ILogger;)V
+	public fun forceSetReplayId (Lio/sentry/protocol/SentryId;)V
 	public fun forceSetSampleRate (Ljava/lang/Double;)V
 	public fun freeze ()V
 	public static fun fromEvent (Lio/sentry/SentryBaseEvent;Ljava/lang/String;Lio/sentry/SentryOptions;)Lio/sentry/Baggage;
@@ -4567,7 +4568,6 @@ public final class io/sentry/TraceContext : io/sentry/JsonSerializable, io/sentr
 	public fun getUserId ()Ljava/lang/String;
 	public fun serialize (Lio/sentry/ObjectWriter;Lio/sentry/ILogger;)V
 	public fun setUnknown (Ljava/util/Map;)V
-	public fun withReplayId (Lio/sentry/protocol/SentryId;)Lio/sentry/TraceContext;
 }
 
 public final class io/sentry/TraceContext$Deserializer : io/sentry/JsonDeserializer {

sentry/src/main/java/io/sentry/Baggage.java

@@ -451,6 +451,13 @@ public void setReplayId(final @Nullable String replayId) {
     set(DSCKeys.REPLAY_ID, replayId);
   }
 
+  @ApiStatus.Internal
+  public void forceSetReplayId(final @NotNull SentryId replayId) {
+    if (!SentryId.EMPTY_ID.equals(replayId)) {
+      keyValues.put(DSCKeys.REPLAY_ID, replayId.toString());
+    }
+  }
+
   @ApiStatus.Internal
   public @Nullable String getOrgId() {
     return get(DSCKeys.ORG_ID);

sentry/src/main/java/io/sentry/SentryClient.java

@@ -250,26 +250,23 @@ private boolean shouldApplyScopeData(final @NotNull CheckIn event, final @NotNul
       }
       if (shouldCaptureReplay) {
         options.getReplayController().captureReplay(event.isCrashed());
-      }
-      if (scope != null && event != null) {
-        final @Nullable SentryId replayId = scope.getReplayId();
-        if (replayId != null && !replayId.equals(SentryId.EMPTY_ID)) {
-          event.getContexts().put(Contexts.REPLAY_ID, replayId.toString());
+        if (scope != null) {
+          final @Nullable SentryId replayId = scope.getReplayId();
+          if (replayId != null && !replayId.equals(SentryId.EMPTY_ID)) {
+            final @Nullable ITransaction transaction = scope.getTransaction();
+            if (transaction != null) {
+              final @Nullable Baggage baggage = transaction.getSpanContext().getBaggage();
+              if (baggage != null) {
+                baggage.forceSetReplayId(replayId);
+              }
+            }
+          }
         }
       }
     }
 
     try {
-      @Nullable TraceContext traceContext = getTraceContext(scope, hint, event);
-      if (traceContext != null && scope != null) {
-        final @Nullable SentryId replayId = scope.getReplayId();
-        if (replayId != null
-            && !replayId.equals(SentryId.EMPTY_ID)
-            && (traceContext.getReplayId() == null
-                || SentryId.EMPTY_ID.equals(traceContext.getReplayId()))) {
-          traceContext = traceContext.withReplayId(replayId);
-        }
-      }
+      final @Nullable TraceContext traceContext = getTraceContext(scope, hint, event);
       final boolean shouldSendAttachments = event != null;
       List<Attachment> attachments = shouldSendAttachments ? getAttachments(hint) : null;
       final @Nullable SentryEnvelope envelope =

sentry/src/main/java/io/sentry/TraceContext.java

@@ -131,24 +131,6 @@ public final class TraceContext implements JsonUnknown, JsonSerializable {
     return replayId;
   }
 
-  @ApiStatus.Internal
-  public @NotNull TraceContext withReplayId(final @NotNull SentryId replayId) {
-    final TraceContext copy =
-        new TraceContext(
-            traceId,
-            publicKey,
-            release,
-            environment,
-            userId,
-            transaction,
-            sampleRate,
-            sampled,
-            replayId,
-            sampleRand);
-    copy.unknown = unknown;
-    return copy;
-  }
-
   // region json
 
   @Nullable