Fix incomplete functionality, nullable warnings, and async issues

Incomplete functionality fixes:
- SkiaEditor: Wire up Completed event to fire on focus lost
- X11InputMethodService: Remove unused _commitCallback field
- SkiaWebView: Set _isProperlyReparented when reparenting succeeds,
  use _lastMainX/_lastMainY to track main window position,
  add _isEmbedded guard to prevent double embedding

Nullable reference fixes:
- Easing: Reorder BounceOut before BounceIn (static init order)
- GestureManager: Use local command variable instead of re-accessing
- SkiaShell: Handle null Title with ?? operator
- GLibNative: Use null! for closure pattern
- LinuxProgramHost: Default title if null
- SkiaWebView.LoadHtml: Add null/empty check for html
- SystemThemeService: Initialize Colors with default values
- DeviceDisplayService/AppInfoService: Use var for nullable env vars
- EmailService: Add null check for message parameter

Async fixes:
- SkiaImage: Use _ = for fire-and-forget async calls
- SystemTrayService: Convert async method without await to sync Task

Reduces warnings from 156 to 133 (remaining are P/Invoke structs
and obsolete MAUI API usage)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Views/SkiaEditor.cs

@@ -982,6 +982,7 @@ public class SkiaEditor : SkiaView
     {
         base.OnFocusLost();
         SkiaVisualStateManager.GoToState(this, SkiaVisualStateManager.CommonStates.Normal);
+        Completed?.Invoke(this, EventArgs.Empty);
     }
 
     #region Selection and Clipboard

Views/SkiaImage.cs

@@ -84,7 +84,7 @@ public class SkiaImage : SkiaView
                 !_pendingSvgReload)
             {
                 _pendingSvgReload = true;
-                ReloadSvgDebounced();
+                _ = ReloadSvgDebounced();
             }
         }
     }
@@ -427,7 +427,7 @@ public class SkiaImage : SkiaView
                 {
                     _lastArrangedBounds = bounds;
                     Console.WriteLine($"[SkiaImage] Arrange detected larger bounds: {width}x{height} vs loaded {_svgLoadedWidth}x{_svgLoadedHeight}");
-                    LoadSvgAtSizeAsync(_currentFilePath, width, height);
+                    _ = LoadSvgAtSizeAsync(_currentFilePath, width, height);
                 }
             }
         }

Views/SkiaShell.cs

@@ -693,7 +693,7 @@ public class SkiaShell : SkiaLayoutView
         }
 
         SetCurrentContent(root.Content);
-        Title = root.Title;
+        Title = root.Title ?? string.Empty;
         Invalidate();
     }
 

Views/SkiaWebView.cs

@@ -759,6 +759,11 @@ public class SkiaWebView : SkiaView
     public void LoadHtml(string html, string? baseUrl = null)
     {
         Console.WriteLine($"[WebView] LoadHtml called, html length: {html?.Length ?? 0}");
+        if (string.IsNullOrEmpty(html))
+        {
+            Console.WriteLine("[WebView] Cannot load HTML - html is null or empty");
+            return;
+        }
         if (!_isInitialized) Initialize();
         if (_webView == IntPtr.Zero || _webkitLoadHtml == null)
         {
@@ -869,6 +874,7 @@ public class SkiaWebView : SkiaView
 
     public void ShowNativeWindow()
     {
+        if (_isEmbedded) return; // Already embedded
         if (!_isInitialized) Initialize();
         if (_gtkWindow == IntPtr.Zero) return;
 
@@ -918,7 +924,15 @@ public class SkiaWebView : SkiaView
         if (gdkWindow != IntPtr.Zero)
         {
             _gtkX11Window = gdk3_x11_window_get_xid(gdkWindow);
-            Console.WriteLine($"[WebView] GTK X11 window: {_gtkX11Window}");
+            if (_gtkX11Window != IntPtr.Zero)
+            {
+                _isProperlyReparented = true;
+                Console.WriteLine($"[WebView] GTK X11 window: {_gtkX11Window} (reparented successfully)");
+            }
+            else
+            {
+                Console.WriteLine($"[WebView] GTK X11 window: failed to get XID");
+            }
         }
 
         PositionUsingGtk();
@@ -1073,13 +1087,20 @@ public class SkiaWebView : SkiaView
         }
         catch { }
 
-        int offsetX = 0, offsetY = 0;
-        int screenX = destX + (int)Bounds.Left - offsetX;
-        int screenY = destY + (int)Bounds.Top - offsetY;
+        // Track main window position changes
+        bool mainWindowMoved = destX != _lastMainX || destY != _lastMainY;
+        if (mainWindowMoved)
+        {
+            _lastMainX = destX;
+            _lastMainY = destY;
+        }
+
+        int screenX = destX + (int)Bounds.Left;
+        int screenY = destY + (int)Bounds.Top;
         int width = Math.Max(100, (int)Bounds.Width);
         int height = Math.Max(100, (int)Bounds.Height);
 
-        if (Math.Abs(screenX - _lastPosX) > 2 || Math.Abs(screenY - _lastPosY) > 2 ||
+        if (mainWindowMoved || Math.Abs(screenX - _lastPosX) > 2 || Math.Abs(screenY - _lastPosY) > 2 ||
             Math.Abs(width - _lastWidth) > 2 || Math.Abs(height - _lastHeight) > 2)
         {
             Console.WriteLine($"[WebView] Move to ({screenX}, {screenY}), size ({width}x{height}), mainWin=({destX},{destY}), bounds=({Bounds.Left},{Bounds.Top})");