feat: add MainWindow wiring query, list, message, and sync

Wires the worker thread, thread list, message pane, sync process and undo
stack together, and replaces the placeholder main() with real startup:
custom URL schemes registered before QApplication, a libnotmuch ABI check,
and config loading.

Four fixes against the drafted version:

- onWorkerError() only set a status label. Its own comment elsewhere
  claimed it reverted the optimistic update, and the spec requires that;
  it did not, so a rejected write left the list showing a tag the database
  never received. The pending change is now recorded and rolled back, and
  a confirmed tagsApplied clears it so a later unrelated error cannot undo
  a write that succeeded.
- runCurrentQuery() cleared the model but left the undo stack pointing at
  rows that no longer exist. Undoing after a new query would have written
  to the database while the visible list stayed put. The stack is cleared
  with the model.
- m_currentMessages was assigned on every thread load and never read.
  Removed.
- buildUi() connected sync output to m_syncLog and errors to m_statusLabel
  before either existed. Both are constructed before the wiring now.

cidPrefix generation lives here, this being its only producer in the
application, and is pinned by tests: it must never contain '!' and must be
distinct per message, which are the invariants the cid: namespacing rests
on. A second test holds registeredActionNames() against
KeyMap::knownActions(), since those two hand-maintained lists drifting
either way silently breaks a user's key binding. Mutation-verified that
dropping an action fails the test by name.

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

1 files changed, 75 insertions, 0 deletions

diff --git a/tests/test_mainwindow.cpp b/tests/test_mainwindow.cpp
new file mode 100644
index 0000000..7b84a60
--- /dev/null
+++ b/tests/test_mainwindow.cpp
@@ -0,0 +1,75 @@
+#include <QtTest>
+
+#include "keymap.h"
+#include "mainwindow.h"
+
+/// MainWindow is mostly wiring and needs a live QApplication plus a real
+/// database, so it is verified manually in Task 13. Two things do not need
+/// either, and both are the kind of drift a comment alone does not prevent.
+class TestMainWindow : public QObject
+{
+    Q_OBJECT
+private slots:
+    void everyKnownActionIsRegistered();
+    void everyRegisteredActionIsKnown();
+    void cidPrefixesAreBangFree();
+    void cidPrefixesAreDistinctPerMessage();
+};
+
+void TestMainWindow::everyKnownActionIsRegistered()
+{
+    // KeyMap::knownActions() is what loadOverrides() validates config bindings
+    // against. An action listed there but never registered means a user can
+    // bind a key in qtmaildir.conf, get no warning, and have it do nothing.
+    const QStringList known = KeyMap::knownActions();
+    const QStringList registered = MainWindow::registeredActionNames();
+
+    for (const QString &action : known) {
+        QVERIFY2(registered.contains(action),
+                 qPrintable(QStringLiteral("known action '%1' is never registered "
+                                           "by MainWindow").arg(action)));
+    }
+}
+
+void TestMainWindow::everyRegisteredActionIsKnown()
+{
+    // The reverse drift: an action MainWindow implements but KeyMap rejects.
+    // The user would get "unknown action" for a binding that is really there.
+    const QStringList known = KeyMap::knownActions();
+    const QStringList registered = MainWindow::registeredActionNames();
+
+    for (const QString &action : registered) {
+        QVERIFY2(known.contains(action),
+                 qPrintable(QStringLiteral("registered action '%1' is not in "
+                                           "KeyMap::knownActions()").arg(action)));
+    }
+}
+
+void TestMainWindow::cidPrefixesAreBangFree()
+{
+    // MainWindow is the only producer of cidPrefix in the application. The
+    // '!' separator that keeps two messages' cid: references apart is only
+    // unambiguous while the prefix half contains none.
+    for (int i : { 0, 1, 9, 10, 99, 1000 }) {
+        const QString prefix = MainWindow::cidPrefixForIndex(i);
+        QVERIFY(!prefix.isEmpty());
+        QVERIFY2(!prefix.contains(QLatin1Char('!')),
+                 qPrintable(QStringLiteral("prefix '%1' contains '!'").arg(prefix)));
+    }
+}
+
+void TestMainWindow::cidPrefixesAreDistinctPerMessage()
+{
+    // Two messages sharing a prefix would share a cid: namespace, which is the
+    // collision the namespacing exists to prevent.
+    QSet<QString> seen;
+    for (int i = 0; i < 200; ++i) {
+        const QString prefix = MainWindow::cidPrefixForIndex(i);
+        QVERIFY2(!seen.contains(prefix),
+                 qPrintable(QStringLiteral("prefix '%1' repeats").arg(prefix)));
+        seen.insert(prefix);
+    }
+}
+
+QTEST_MAIN(TestMainWindow)
+#include "test_mainwindow.moc"