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>

src/settings/Settings.cpp

@@ -0,0 +1,42 @@
+#include "Settings.h"
+
+#include <QSettings>
+
+namespace {
+constexpr auto AutoCapitalizeKey = "typing/autoCapitalize";
+constexpr auto DoubleSpacePeriodKey = "typing/doubleSpacePeriod";
+}
+
+Settings::Settings(QObject *parent)
+    : QObject(parent)
+{
+    const QSettings store;
+    const TypingOptions defaults;
+    m_typing.autoCapitalize = store.value(AutoCapitalizeKey, defaults.autoCapitalize).toBool();
+    m_typing.doubleSpacePeriod = store.value(DoubleSpacePeriodKey, defaults.doubleSpacePeriod).toBool();
+}
+
+void Settings::setAutoCapitalize(bool enabled)
+{
+    TypingOptions options = m_typing;
+    options.autoCapitalize = enabled;
+    setTypingOptions(options);
+}
+
+void Settings::setDoubleSpacePeriod(bool enabled)
+{
+    TypingOptions options = m_typing;
+    options.doubleSpacePeriod = enabled;
+    setTypingOptions(options);
+}
+
+void Settings::setTypingOptions(const TypingOptions &options)
+{
+    if (options == m_typing)
+        return;
+    m_typing = options;
+    QSettings store;
+    store.setValue(AutoCapitalizeKey, m_typing.autoCapitalize);
+    store.setValue(DoubleSpacePeriodKey, m_typing.doubleSpacePeriod);
+    Q_EMIT typingOptionsChanged();
+}

src/settings/Settings.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "input/TypingOptions.h"
+
+#include <QObject>
+#include <QtQml/qqmlregistration.h>
+
+// User preferences, persisted with QSettings (~/.config/sloposk/sloposk.conf)
+// and editable from the keyboard's settings panel.
+class Settings : public QObject
+{
+    Q_OBJECT
+    QML_ELEMENT
+    QML_UNCREATABLE("Created in C++")
+    Q_PROPERTY(bool autoCapitalize READ autoCapitalize WRITE setAutoCapitalize NOTIFY typingOptionsChanged)
+    Q_PROPERTY(bool doubleSpacePeriod READ doubleSpacePeriod WRITE setDoubleSpacePeriod NOTIFY typingOptionsChanged)
+
+public:
+    explicit Settings(QObject *parent = nullptr);
+
+    TypingOptions typingOptions() const { return m_typing; }
+
+    bool autoCapitalize() const { return m_typing.autoCapitalize; }
+    void setAutoCapitalize(bool enabled);
+    bool doubleSpacePeriod() const { return m_typing.doubleSpacePeriod; }
+    void setDoubleSpacePeriod(bool enabled);
+
+Q_SIGNALS:
+    void typingOptionsChanged();
+
+private:
+    void setTypingOptions(const TypingOptions &options);
+
+    TypingOptions m_typing;
+};