Improve bundling error message formatting (#55794)

Summary:
Pull Request resolved: #55794

Format the error messages coming from bundling to mainting the formatting and make these easier to read.

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D94611951

fbshipit-source-id: cbb8b2d1ff517b5487d4b799b1e2e3476629f84c

Author: Nick Lefever

private/react-native-fantom/runner/bundling.js

@@ -52,9 +52,19 @@ export async function createBundle(options: BundleOptions): Promise<void> {
   );
 
   if (lastBundleError || lastBundleResult?.ok !== true) {
-    throw new Error(
-      `Failed to request bundle from Metro: ${lastBundleError?.message ?? (await lastBundleResult?.text()) ?? ''}`,
-    );
+    let errorMessage =
+      lastBundleError?.message ?? (await lastBundleResult?.text()) ?? '';
+
+    try {
+      const parsed = JSON.parse(errorMessage);
+      if (typeof parsed.message === 'string') {
+        errorMessage = parsed.message;
+      }
+    } catch {
+      // Not JSON — use the raw text as-is.
+    }
+
+    throw new Error(`Failed to request bundle from Metro:\n${errorMessage}`);
   }
 
   await fs.promises.writeFile(