fix(testrun): point the device java preflight hint at the ios-device doctor

internal/testrun/preflight.go

@@ -56,11 +56,17 @@ func runPreflight(ctx context.Context, platform string, check preflightFunc) err
 // know a run targets a physical iOS device. Android already requires java in
 // the top-level Preflight, so this only matters for ios.
 func preflightDevice(platform string) error {
+	return runPreflightDevice(platform, preflightCheck)
+}
+
+func runPreflightDevice(platform string, check preflightFunc) error {
 	if platform != "ios" {
 		return nil
 	}
-	if err := preflightCheck("java"); err != nil {
-		return preflightFailure("ios", err)
+	if err := check("java"); err != nil {
+		// The doctor splits simulator and device checks: java lives under the
+		// ios-device platform, so the hint must point there.
+		return preflightFailure("ios-device", err)
 	}
 	return nil
 }

internal/testrun/preflight_test.go

@@ -101,6 +101,22 @@ func TestPreflightDevice_NonIosIsNoop(t *testing.T) {
 	}
 }
 
+func TestPreflightDevice_JavaFailurePointsAtIosDeviceDoctor(t *testing.T) {
+	check := func(name string) error {
+		if name == "java" {
+			return errors.New("java not found")
+		}
+		return nil
+	}
+	err := runPreflightDevice("ios", check)
+	if err == nil || !strings.Contains(err.Error(), "java") {
+		t.Fatalf("expected java error, got %v", err)
+	}
+	if !strings.Contains(err.Error(), "sanderling doctor --platform=ios-device") {
+		t.Errorf("hint must name the ios-device doctor platform: %v", err)
+	}
+}
+
 func TestPreflight_UnknownPlatform(t *testing.T) {
 	check := func(string) error { return nil }
 	if err := runPreflight(context.Background(), "fuchsia", check); err == nil {