Full keyboard mode, Ctrl/Alt/Super, dead keys, shift levels

- Full (iPad Pro) mode: every typing key from the keymap, number row,
  tab, caps lock, ctrl/super/alt; shifted symbol shown above and flickable
- Dead keys compose with the locale's XKB compose table
- Ctrl/Alt/Super stick like shift and turn keys into shortcuts; a tapped
  or held shift joins shortcuts and non-text keys, auto-shift and caps
  lock don't
- Auto-capitalization and caps lock only capitalize letters; the user's
  shift picks the keymap's shifted level
- Mode switch in settings keeps key size by resizing the window

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

tests/tst_layoutbuilder.cpp

@@ -1,6 +1,7 @@
 #include "TestLayouts.h"
 
 #include <QTest>
+#include <xkbcommon/xkbcommon-keysyms.h>
 
 using namespace Qt::StringLiterals;
 
@@ -90,6 +91,37 @@ private Q_SLOTS:
         QVERIFY(a.contains(u"á"_s));
     }
 
+    void fullModeHasEveryTypingKey()
+    {
+        const Layout us = TestLayouts::build("us", KeyboardMode::Full);
+        const auto labels = [&](int row) {
+            QString text;
+            for (const KeyDef &key : us.layers.first().rows[row]) {
+                if (key.type == KeyType::Character)
+                    text += key.label;
+            }
+            return text;
+        };
+        QCOMPARE(labels(0), u"`1234567890-=");
+        QCOMPARE(labels(1), u"qwertyuiop[]\\");
+        QCOMPARE(labels(2), u"asdfghjkl;'");
+        QCOMPARE(labels(3), u"zxcvbnm,./"); // LSGT (< >) repeats , . shifted: left out
+        QCOMPARE(letterKey(us, u"1"_s).flick, u"!");
+        QCOMPARE(letterKey(us, u"1"_s).shifted, u"!");
+    }
+
+    void fullModeKeepsDeadKeysAndKeymapShift()
+    {
+        const Layout sk = TestLayouts::build("sk", KeyboardMode::Full);
+        const KeyDef &acute = letterKey(sk, u"´"_s);
+        QCOMPARE(acute.dead, quint32(XKB_KEY_dead_acute));
+        QCOMPARE(acute.deadShifted, quint32(XKB_KEY_dead_caron));
+        QCOMPARE(letterKey(sk, u"ô"_s).shifted, u"\""); // as the physical key
+        QCOMPARE(letterKey(sk, u"ľ"_s).shifted, u"2");
+        // ľ has its own key now, so it's not a long-press choice on l.
+        QVERIFY(!letterKey(sk, u"l"_s).alternates.contains(u"ľ"_s));
+    }
+
     void noPlaceholdersRemain()
     {
         for (const Layer &layer : TestLayouts::build("us").layers) {