Add Windows window-minimize guard

internal/enforce/guard_other.go

@@ -1,4 +1,4 @@
-//go:build !linux
+//go:build !linux && !windows
 
 package enforce
 

internal/enforce/windows.go

@@ -0,0 +1,21 @@
+//go:build windows
+
+package enforce
+
+import (
+	"context"
+
+	"antidrift/internal/winapi"
+)
+
+// NewGuard returns the Windows window-minimize guard.
+func NewGuard() Guard { return windowsGuard{} }
+
+type windowsGuard struct{}
+
+// MinimizeActive minimizes the current foreground window. It is best-effort:
+// with nothing focused it does nothing and returns nil. Stateless and per-call,
+// mirroring the short-lived X11 connection model.
+func (windowsGuard) MinimizeActive(context.Context) error {
+	return winapi.MinimizeForeground()
+}