fix(test): Handle malformed xcresult summaries

Return null when xcresult summary parsing receives malformed JSON so the
exported parser matches its nullable contract and callers can safely fall
back to streamed counts.

Refs #397
Co-Authored-By: Codex <noreply@openai.com>

Author: cameroncooke

src/utils/__tests__/xcresult-test-failures.test.ts

@@ -27,6 +27,11 @@ describe('parseXcresultTestSummaryCounts', () => {
       skipped: 0,
     });
   });
+
+  it('returns null for malformed JSON summary output', () => {
+    expect(parseXcresultTestSummaryCounts('warning: no summary available')).toBeNull();
+    expect(parseXcresultTestSummaryCounts('')).toBeNull();
+  });
 });
 
 describe('parseXcresultFailureMessage', () => {

src/utils/xcresult-test-failures.ts

@@ -27,7 +27,17 @@ function isSummaryCount(value: unknown): value is number {
 }
 
 export function parseXcresultTestSummaryCounts(raw: string): Counts | null {
-  const summary = JSON.parse(raw) as XcresultTestSummary;
+  let summary: XcresultTestSummary;
+  try {
+    const parsed = JSON.parse(raw) as unknown;
+    if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) {
+      return null;
+    }
+    summary = parsed as XcresultTestSummary;
+  } catch {
+    return null;
+  }
+
   const { passedTests, failedTests, skippedTests } = summary;
 
   if (