Add SFTP toggle button to SSH tabs and enable fullscreen support

- Added 📁 folder icon button on SSH tabs to toggle the SFTP file browser
- Button appears on hover/active, styled consistently with the close button
- Removed conflicting Cmd+Shift+F shortcut (clashes with macOS find)
- Added platform-specific window options (Mac, Windows, Linux)
- Added F11 fullscreen toggle and Escape to exit fullscreen
- Cleaned up SFTP panel on session close

main.go

@@ -8,6 +8,9 @@ import (
 	"github.com/wailsapp/wails/v2"
 	"github.com/wailsapp/wails/v2/pkg/options"
 	"github.com/wailsapp/wails/v2/pkg/options/assetserver"
+	"github.com/wailsapp/wails/v2/pkg/options/linux"
+	"github.com/wailsapp/wails/v2/pkg/options/mac"
+	"github.com/wailsapp/wails/v2/pkg/options/windows"
 
 	application "github.com/copilot-ssh-client/app/internal/app"
 	"github.com/copilot-ssh-client/app/frontend"
@@ -32,6 +35,17 @@ func main() {
 		OnStartup:        nexus.Startup,
 		OnShutdown:       nexus.Shutdown,
 		OnDomReady:       nexus.DomReady,
+		// macOS: enable the green fullscreen traffic-light button.
+		Mac: &mac.Options{
+			About: &mac.AboutInfo{
+				Title:   "Nexus Terminal",
+				Message: "A premium desktop terminal client",
+			},
+		},
+		// Windows: default decorations include maximise; fullscreen via F11.
+		Windows: &windows.Options{},
+		// Linux: use the default window manager decorations (fullscreen via WM).
+		Linux: &linux.Options{},
 		Bind: []interface{}{
 			nexus.APIService(),
 		},