Fix main menu layout alignment issue

- Replace layout.NewHBoxLayout() with container.NewHBox() for header
- Replace layout.NewVBoxLayout() with container.NewVBox() for body
- Prevents unwanted stretching and improves alignment with rest of UI
- Elements now use natural sizing instead of filling available space

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

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

internal/ui/mainmenu.go

@@ -68,7 +68,7 @@ func BuildMainMenu(modules []ModuleInfo, onModuleClick func(string), onModuleDro
 	logsBtn := widget.NewButton("Logs", onLogsClick)
 	logsBtn.Importance = widget.LowImportance
 
-	header := container.New(layout.NewHBoxLayout(), title, layout.NewSpacer(), sidebarToggleBtn, benchmarkBtn, viewResultsBtn, logsBtn, queueTile)
+	header := container.NewHBox(title, layout.NewSpacer(), sidebarToggleBtn, benchmarkBtn, viewResultsBtn, logsBtn, queueTile)
 
 	categorized := map[string][]fyne.CanvasObject{}
 	for i := range modules {
@@ -106,7 +106,7 @@ func BuildMainMenu(modules []ModuleInfo, onModuleClick func(string), onModuleDro
 	padding := canvas.NewRectangle(color.Transparent)
 	padding.SetMinSize(fyne.NewSize(0, 14))
 
-	body := container.New(layout.NewVBoxLayout(),
+	body := container.NewVBox(
 		header,
 		padding,
 		container.NewVBox(sections...),