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_layoutloader.cpp

@@ -1,22 +1,11 @@
+#include "TestLayouts.h"
+#include "layout/KeyGeometry.h"
 #include "layout/LayoutLoader.h"
-#include "layout/LayoutRepository.h"
 
 #include <QTest>
 
 using namespace Qt::StringLiterals;
 
-namespace {
-
-qreal rowUnits(const Row &row)
-{
-    qreal units = 0;
-    for (const KeyDef &key : row)
-        units += key.width;
-    return units;
-}
-
-} // namespace
-
 class TestLayoutLoader : public QObject
 {
     Q_OBJECT
@@ -65,24 +54,35 @@ private Q_SLOTS:
         QVERIFY(!LayoutLoader::validate(*layout, &error));
     }
 
-    void builtinLayoutsAreConsistent()
+    void templateIsValid()
     {
-        Q_INIT_RESOURCE(layouts);
-        LayoutRepository repo;
-        repo.loadDirectory(u":/layouts"_s);
-        repo.finalize({});
-        QVERIFY(repo.indexOf(u"en-US"_s) >= 0);
-        QVERIFY(repo.indexOf(u"sv-SE"_s) >= 0);
+        QString error;
+        QVERIFY2(LayoutLoader::validate(TestLayouts::builtinTemplate(), &error), qPrintable(error));
+    }
 
-        for (const Layout &layout : repo.layouts()) {
-            QVERIFY2(layout.layer(u"numbers"_s), qPrintable(layout.id)); // sv-SE gets it from its base
-            for (const Layer &layer : layout.layers) {
-                const qreal expected = rowUnits(layer.rows.first());
-                for (const Row &row : layer.rows) {
-                    QVERIFY2(qFuzzyCompare(rowUnits(row), expected),
-                             qPrintable(u"%1/%2: rows differ in width"_s.arg(layout.id, layer.name)));
-                }
-            }
+    void rejectsLettersWithoutRow()
+    {
+        QString error;
+        QVERIFY(!LayoutLoader::parse(R"({"id": "t", "layers": [{"name": "l", "rows": [[{"type": "letters"}]]}]})",
+                                     &error));
+    }
+
+    // Stretching must even out rows whatever the keymap's letter counts.
+    void builtLayersHaveEqualRows_data()
+    {
+        QTest::addColumn<QString>("xkbLayout");
+        for (const char *layout : {"us", "sk", "se", "de", "fr", "ru", "gr"})
+            QTest::newRow(layout) << QString::fromLatin1(layout);
+    }
+
+    void builtLayersHaveEqualRows()
+    {
+        QFETCH(QString, xkbLayout);
+        const Layout layout = TestLayouts::build(qPrintable(xkbLayout));
+        for (const Layer &layer : layout.layers) {
+            const qreal expected = rowUnits(layer.rows.first());
+            for (const Row &row : layer.rows)
+                QVERIFY2(qFuzzyCompare(rowUnits(row), expected), qPrintable(layer.name));
         }
     }
 };