fix: open a conversation's first message from the overview

Clicking the first message in a conversation overview's unread list did
nothing visible. applyPendingDashboardSelection() matched the
conversation row on the root's message id, so it reselected the row that
was already current and the overview stayed on screen. Since item 177
setThreadMessages keeps a conversation's first message as child 0, so
it has a row of its own. Only a thread of one now answers for its
message on its own row, the same guard 236ac86 added to the recovery.

AGENTS.md still said a thread's first message is never among its
children, which has been true only for a thread of one since item 177.
It is corrected to say so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/tests/test_mainwindow.cpp b/tests/test_mainwindow.cpp
index 0aaf8ff..7ef89e7 100644
--- a/tests/test_mainwindow.cpp
+++ b/tests/test_mainwindow.cpp
@@ -390,6 +390,7 @@ private slots:
     void recoveringAStaleThreadQueriesTheWholeThread();
     void recoveryReselectsTheMessageThatWasBeingRead();
     void recoveryOnTheFirstMessageSelectsItsOwnRow();
+    void aDashboardEntryForTheFirstMessageSelectsItsOwnRow();
     void doubleClickingAThreadOpensThatThreadAlone();
     void doubleClickingAReplyOpensItsThreadNotTheReplyAlone();
     void doubleClickingDoesNotLeaveTheMarkReadTimerArmed();
@@ -3538,6 +3539,60 @@ void TestMainWindow::recoveryOnTheFirstMessageSelectsItsOwnRow()
     QCOMPARE(model->threadFor(current).threadId, QStringLiteral("T1"));
 }
 
+void TestMainWindow::aDashboardEntryForTheFirstMessageSelectsItsOwnRow()
+{
+    // The dashboard's unread list can name the conversation's FIRST message.
+    // Since item 177 that message is child 0 with a row of its own, so the
+    // entry must land there. Matching the conversation row on the root's id
+    // reselected the row already current, and the click did nothing visible.
+    const Config config;
+    MainWindow window(config);
+
+    auto *queryEdit = window.findChild<QLineEdit *>();
+    QVERIFY(queryEdit);
+    queryEdit->setText(QStringLiteral("tag:unread"));
+    queryEdit->returnPressed();
+    const quint64 generation = window.currentGenerationForTesting();
+
+    auto *model = window.findChild<ThreadListModel *>();
+    QVERIFY(model);
+    auto *view = window.findChild<ThreadListView *>();
+    QVERIFY(view);
+
+    ThreadSummary thread = makeThread(QStringLiteral("T1"), {});
+    thread.totalCount = 2;
+    const QVector<ThreadSummary> result{ thread };
+    QMetaObject::invokeMethod(&window, "onThreadsReady",
+                              Q_ARG(QVector<ThreadSummary>, result),
+                              Q_ARG(quint64, generation));
+    view->setCurrentIndex(model->index(0, 0, QModelIndex()));
+    QVERIFY(model->isConversationRow(view->currentIndex()));
+
+    QMetaObject::invokeMethod(&window, "selectMessageInCurrentThread",
+                              Q_ARG(QString, QStringLiteral("m0@example.org")));
+
+    MessageNode root;
+    root.messageId = QStringLiteral("m0@example.org");
+    root.threadId = QStringLiteral("T1");
+    root.depth = 0;
+    MessageNode reply;
+    reply.messageId = QStringLiteral("m1@example.org");
+    reply.threadId = QStringLiteral("T1");
+    reply.depth = 1;
+    const QVector<MessageNode> nodes{ root, reply };
+    QMetaObject::invokeMethod(&window, "onThreadTreeLoaded",
+                              Q_ARG(QVector<MessageNode>, nodes),
+                              Q_ARG(quint64, generation));
+
+    const QModelIndex current = view->currentIndex();
+    QVERIFY2(current.isValid(), "the entry selected nothing");
+    QVERIFY2(model->isMessageRow(current),
+             "the first message landed on the conversation row, which keeps "
+             "the dashboard on screen");
+    QCOMPARE(model->messageAt(current).messageId,
+             QStringLiteral("m0@example.org"));
+}
+
 void TestMainWindow::doubleClickingAThreadOpensThatThreadAlone()
 {
     // Item 91, the thread case: "double click on a thread loads the whole