refactor(testrun): defer the java preflight check to the physical-device path

internal/testrun/preflight.go

@@ -41,18 +41,30 @@ func runPreflight(ctx context.Context, platform string, check preflightFunc) err
 		}
 		return nil
 	case "ios":
+		// Simulator runs drive the native companion and need no JVM. The java
+		// requirement is deferred to the physical-device path in buildDriver.
 		if err := check("xcrun"); err != nil {
 			return preflightFailure("ios", err)
 		}
-		if err := check("java"); err != nil {
-			return preflightFailure("ios", err)
-		}
 		return nil
 	default:
 		return fmt.Errorf("preflight: unknown platform %q", platform)
 	}
 }
 
+// preflightDevice runs the extra host checks the JVM sidecar path needs once we
+// 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 {
+	if platform != "ios" {
+		return nil
+	}
+	if err := preflightCheck("java"); err != nil {
+		return preflightFailure("ios", err)
+	}
+	return nil
+}
+
 func preflightFailure(platform string, cause error) error {
 	return fmt.Errorf(
 		"preflight: %w\nrun `sanderling doctor --platform=%s` for full host-readiness checks",