fix: sign entry crash and remove blocking callback workaround

- Initialize m_iEditingLine to 0 in SignEntryMenu constructor
  (was uninitialized, causing out-of-bounds array access)
- Add bounds check on m_iEditingLine before array access in callback
- Only truncate sign text if longer than 15 chars (avoid padding)
- Remove manual KeyboardCompleteSeedCallback call in
  LaunchMoreOptionsMenu (no longer needed since RequestKeyboard
  now fires callbacks asynchronously from Tick)

Minecraft.Client/Platform/Common/UI/UIScene_SignEntryMenu.cpp

@@ -18,6 +18,7 @@ UIScene_SignEntryMenu::UIScene_SignEntryMenu(int iPad, void* _initData,
     SignEntryScreenInput* initData = (SignEntryScreenInput*)_initData;
     m_sign = initData->sign;
 
+    m_iEditingLine = 0;
     m_bConfirmed = false;
     m_bIgnoreInput = false;
 
@@ -141,12 +142,12 @@ int UIScene_SignEntryMenu::KeyboardCompleteCallback(void* lpParam, bool bRes) {
     // 4J HEG - No reason to set value if keyboard was cancelled
     UIScene_SignEntryMenu* pClass = (UIScene_SignEntryMenu*)lpParam;
     pClass->m_bIgnoreInput = false;
-    if (bRes) {
+    if (bRes && pClass->m_iEditingLine >= 0 && pClass->m_iEditingLine < 4) {
         uint16_t pchText[128];
         ZeroMemory(pchText, 128 * sizeof(uint16_t));
         InputManager.GetText(pchText);
         std::wstring str = uint16_to_wstring(pchText);
-        str.resize(15);
+        if (str.size() > 15) str.resize(15);
         pClass->m_textInputLines[pClass->m_iEditingLine].setLabel(str);
     }
     return 0;