fix(github_graphql): set the merged flag on pull requests

The GraphQL extractor filled MergedAt, MergedBy and MergeCommit but never
Merged, so every pull request collected through GraphQL is stored with
merged = false, including the merged ones. #8573 fixed the same gap on the
REST side; the GraphQL extractor was not part of it.

The flag is derived from mergedAt, which GitHub sets exactly when a pull
request is merged, so rows already sitting in the raw layer are repaired by
re-running the extractor and no re-collect is needed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: zyv4yk

backend/plugins/github_graphql/tasks/pr_extractor.go

@@ -171,6 +171,7 @@ func convertGithubPullRequest(pull *GraphqlQueryPr, connId uint64, repoId int) (
 		GithubUpdatedAt: pull.UpdatedAt,
 		ClosedAt:        pull.ClosedAt,
 		MergedAt:        pull.MergedAt,
+		Merged:          pull.MergedAt != nil, // mergedAt is set exactly when a pull request is merged
 		Body:            pull.Body,
 		BaseRef:         pull.BaseRefName,
 		BaseCommitSha:   pull.BaseRefOid,

backend/plugins/github_graphql/tasks/pr_extractor_test.go

@@ -0,0 +1,56 @@
+/*
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements.  See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to You under the Apache License, Version 2.0
+(the "License"); you may not use this file except in compliance with
+the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package tasks
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConvertGithubPullRequestMerged(t *testing.T) {
+	mergedAt := time.Date(2026, 8, 14, 10, 0, 0, 0, time.UTC)
+
+	merged, err := convertGithubPullRequest(&GraphqlQueryPr{
+		DatabaseId: 1,
+		Number:     1,
+		State:      `MERGED`,
+		MergedAt:   &mergedAt,
+		ClosedAt:   &mergedAt,
+	}, 1, 1)
+	assert.Nil(t, err)
+	assert.True(t, merged.Merged)
+
+	closed, err := convertGithubPullRequest(&GraphqlQueryPr{
+		DatabaseId: 2,
+		Number:     2,
+		State:      `CLOSED`,
+		ClosedAt:   &mergedAt,
+	}, 1, 1)
+	assert.Nil(t, err)
+	assert.False(t, closed.Merged)
+
+	open, err := convertGithubPullRequest(&GraphqlQueryPr{
+		DatabaseId: 3,
+		Number:     3,
+		State:      `OPEN`,
+	}, 1, 1)
+	assert.Nil(t, err)
+	assert.False(t, open.Merged)
+}