Fix persisting the size of a focus mode window (microsoft#17068)

While I was fixing the initial position thing, I figured I'd fix this
too. We were mistakenly accounting for the size of the titlebar when we
should launch into focus mode (without one)

Closes microsoft#10730

Author: zadjii-msft

src/cascadia/TerminalApp/TerminalWindow.cpp

@@ -562,9 +562,21 @@ namespace winrt::TerminalApp::implementation
     {
         winrt::Windows::Foundation::Size proposedSize{};
 
+        // In focus mode, we don't want to include our own tab row in the size
+        // of the window that we hand back. So we account for passing
+        // --focusMode on the commandline here, and the mode in the settings.
+        // Below, we'll also account for if focus mode was persisted into the
+        // session for restoration.
+        bool focusMode = _appArgs.GetLaunchMode().value_or(_settings.GlobalSettings().LaunchMode()) == LaunchMode::FocusMode;
+
         const auto scale = static_cast<float>(dpi) / static_cast<float>(USER_DEFAULT_SCREEN_DPI);
         if (const auto layout = LoadPersistedLayout())
         {
+            if (layout.LaunchMode())
+            {
+                focusMode = layout.LaunchMode().Value() == LaunchMode::FocusMode;
+            }
+
             if (layout.InitialSize())
             {
                 proposedSize = layout.InitialSize().Value();
@@ -602,7 +614,7 @@ namespace winrt::TerminalApp::implementation
         // GH#2061 - If the global setting "Always show tab bar" is
         // set or if "Show tabs in title bar" is set, then we'll need to add
         // the height of the tab bar here.
-        if (_settings.GlobalSettings().ShowTabsInTitlebar())
+        if (_settings.GlobalSettings().ShowTabsInTitlebar() && !focusMode)
         {
             // In the past, we used to actually instantiate a TitlebarControl
             // and use Measure() to determine the DesiredSize of the control, to
@@ -620,7 +632,7 @@ namespace winrt::TerminalApp::implementation
             static constexpr auto titlebarHeight = 40;
             proposedSize.Height += (titlebarHeight)*scale;
         }
-        else if (_settings.GlobalSettings().AlwaysShowTabs())
+        else if (_settings.GlobalSettings().AlwaysShowTabs() && !focusMode)
         {
             // Same comment as above, but with a TabRowControl.
             //