Fix double-space period, shift double-tap; settings; letters from system keymap

- Double-space replaced the space via a Backspace keysym, which clients
  apply after the commit: use delete_surrounding_text with the commit
- Tests use a shared FakeEngine that applies ops to a simulated field
- Double-tap shift locks at a sentence start; typing between taps doesn't
- Organization name set: config lives in ~/.config/sloposk/
- Settings (auto-capitalization, double-space period) with a ⚙ panel
- Letter rows come from the compositor's XKB keymap; other letters of the
  layout become long-press alternates; globe switches the system layout
  over org.kde.keyboard
- One JSON template for non-letter layers; stretch keys even out rows

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

tests/tst_keyboardsurface.cpp

@@ -1,11 +1,11 @@
 // End-to-end gesture tests: real Keyboard.qml, synthetic touch events.
 // Set SLOPOSK_SNAPSHOT_DIR to also save what the keyboard looks like mid-gesture.
 
-#include "engine/InputEngine.h"
+#include "FakeEngine.h"
 #include "input/KeyboardController.h"
 #include "input/KeyboardSurface.h"
 #include "layout/LayoutModel.h"
-#include "layout/LayoutRepository.h"
+#include "TestLayouts.h"
 
 #include <QQmlComponent>
 #include <QQmlEngine>
@@ -21,21 +21,6 @@ using namespace Qt::StringLiterals;
 
 namespace {
 
-class FakeEngine : public InputEngine
-{
-public:
-    void commitText(const QString &text) override { output += text; }
-    void sendKeysym(quint32 keysym, Qt::KeyboardModifiers modifiers) override
-    {
-        keysyms.append(keysym);
-        lastModifiers = modifiers;
-    }
-
-    QString output;
-    QList<quint32> keysyms;
-    Qt::KeyboardModifiers lastModifiers;
-};
-
 constexpr QPoint KeyboardOffset(0, 100); // room above for popups
 constexpr int LongPressWaitMs = 600;
 
@@ -47,7 +32,6 @@ class TestKeyboardSurface : public QObject
 
 private:
     FakeEngine engine;
-    LayoutRepository repo;
     LayoutModel model;
     std::unique_ptr<KeyboardController> controller;
     QQmlEngine qml;
@@ -81,10 +65,8 @@ private:
 private Q_SLOTS:
     void initTestCase()
     {
-        Q_INIT_RESOURCE(layouts);
-        repo.loadDirectory(u":/layouts"_s);
-        repo.finalize(u"en_US"_s);
-        controller = std::make_unique<KeyboardController>(engine, model, repo);
+        model.setLayout(TestLayouts::build("us"));
+        controller = std::make_unique<KeyboardController>(engine, model);
 
         QQmlComponent component(&qml, "Sloposk", "Keyboard");
         keyboard = qobject_cast<QQuickItem *>(component.createWithInitialProperties({