feat: add native Windows hierarchy test harness

internal/client/supervisor/windows/native_exec.go

@@ -43,7 +43,13 @@ type NativeOptions struct {
 	MaxWrapperBytes  uint64
 	MaxOutputChunk   uint64
 	WindowsTermGrace time.Duration
-	Now              func() time.Time
+	// TestContextFailures is populated only by the separately tagged native
+	// fixture binary.  It is deliberately not protocol or TOML policy: it lets
+	// the fixture fail token preparation before launch so the real daemon can
+	// prove its fallback order without creating a second broker or weakening a
+	// release binary.
+	TestContextFailures map[ExecutionContext]bool
+	Now                 func() time.Time
 }
 
 // JobProfile is the validated administrator policy for one protocol profile.