cmd/drover: replace MessageBox stub with Wails GUI (internal/gui.Run)

Bare 'drover' (and 'drover gui') no longer pop a Win32 MessageBox —
they hand off to internal/gui which mounts a real Wails window with
the Classic React variant. The old gui_windows.go / gui_other.go
files are removed; their job is now done by internal/gui/run.go.

Auto-update on startup is unchanged — still runs before gui.Run().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/drover/main.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"git.okcu.io/root/drover-go/internal/gui"
 	"git.okcu.io/root/drover-go/internal/updater"
 )
 
@@ -46,13 +47,12 @@ func newRootCmd() *cobra.Command {
 		SilenceUsage:  true,
 		SilenceErrors: false,
 		// No subcommand and no flags = end-user double-clicked the exe.
-		// First do a quick update check (silent if no network or already
-		// current); if an update is available we prompt, apply, and
-		// re-launch ourselves. Then show the smoke-test window.
+		// First do a quick silent update check (no-op if offline or
+		// already current); if an update is available we apply it and
+		// re-launch ourselves. Then we open the Wails-backed GUI.
 		RunE: func(cmd *cobra.Command, args []string) error {
 			autoUpdateOnStartup()
-			showTestWindow()
-			return nil
+			return gui.Run(Version)
 		},
 	}
 
@@ -72,10 +72,9 @@ func newRootCmd() *cobra.Command {
 func newGUICmd() *cobra.Command {
 	return &cobra.Command{
 		Use:   "gui",
-		Short: "Show a test window (smoke check that the binary launches on this machine)",
+		Short: "Open the Drover-Go window (same as launching the exe with no args)",
 		RunE: func(cmd *cobra.Command, args []string) error {
-			showTestWindow()
-			return nil
+			return gui.Run(Version)
 		},
 	}
 }