Optional PC key blocks: function row, navigation, numeric keypad

- Template sections placed above or to the right of the typing keys;
  the user picks any mix in settings, typing keys included
- keysym keys send XKB keysyms on press, optionally repeating
- Geometry lays blocks side by side with one key unit; stretch keys are
  resolved at layout time so composed blocks line up
- Toggling a block resizes the window so keys keep their size

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

tests/tst_controller.cpp

@@ -42,6 +42,7 @@ private Q_SLOTS:
     {
         engine = {};
         model.setLayout(TestLayouts::build("us"));
+        model.setVisibleSections({MainSectionId});
         controller = std::make_unique<KeyboardController>(engine, model);
     }
 
@@ -199,6 +200,36 @@ private Q_SLOTS:
         QCOMPARE(requested, 1);
     }
 
+    void keysymKeyActsOnPressAndRepeats()
+    {
+        KeyDef left = makeKey(KeyType::Keysym, u"←"_s);
+        left.keysym = XKB_KEY_Left;
+        left.repeat = true;
+        controller->keyDown(left, 0);
+        QCOMPARE(engine.keysyms, QList<quint32>{XKB_KEY_Left});
+        QTRY_VERIFY_WITH_TIMEOUT(engine.keysyms.size() >= 3, 2000); // held: repeats
+        controller->keyUp(left, KeyOutput::Primary, {}, 0);
+        const auto sent = engine.keysyms.size();
+        QTest::qWait(200);
+        QCOMPARE(engine.keysyms.size(), sent);
+        QVERIFY(engine.output.isEmpty()); // no text
+    }
+
+    void sectionsAreComposedAroundTheMainKeys()
+    {
+        const qsizetype mainKeys = model.rowCount();
+        const qreal mainUnits = model.totalUnits();
+        model.setVisibleSections({MainSectionId, u"function"_s});
+        QCOMPARE(model.rowCount(), mainKeys + 13);
+        QCOMPARE(model.totalUnits(), mainUnits); // above, not beside
+        model.setVisibleSections({MainSectionId, u"navigation"_s});
+        QCOMPARE(model.totalUnits(), mainUnits + 3);
+        model.setVisibleSections({u"numpad"_s});
+        QCOMPARE(model.rowCount(), 19);
+        model.setVisibleSections({});
+        QCOMPARE(model.rowCount(), mainKeys); // never nothing
+    }
+
     void dismissEmitsSignal()
     {
         int dismissed = 0;