test(core): Add integration test for getTracingHeadersForFetchRequest

This adds an integration test that demonstrates cross-package usage of the
getTracingHeadersForFetchRequest function exported from @sentry/core.

The test validates that the function correctly generates tracing headers
(sentry-trace and baggage) when called from another package within an
active span context.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: cursoragent

dev-packages/node-integration-tests/suites/public-api/getTracingHeadersForFetchRequest/basic-usage/scenario.ts

@@ -0,0 +1,30 @@
+import * as Sentry from '@sentry/node';
+import { getTracingHeadersForFetchRequest } from '@sentry/core';
+import { loggingTransport } from '@sentry-internal/node-integration-tests';
+
+Sentry.init({
+  dsn: 'https://public@dsn.ingest.sentry.io/1337',
+  tracesSampleRate: 1.0,
+  transport: loggingTransport,
+});
+
+Sentry.startSpan({ name: 'test-span' }, () => {
+  const headers = getTracingHeadersForFetchRequest('https://example.com/api', {});
+
+  if (!headers || typeof headers !== 'object' || Array.isArray(headers)) {
+    throw new Error('getTracingHeadersForFetchRequest returned invalid headers');
+  }
+
+  const sentryTrace = 'sentry-trace' in headers ? headers['sentry-trace'] : undefined;
+  const baggage = 'baggage' in headers ? headers.baggage : undefined;
+
+  if (!sentryTrace || typeof sentryTrace !== 'string' || !sentryTrace.match(/^[0-9a-f]{32}-[0-9a-f]{16}-[01]$/)) {
+    throw new Error('sentry-trace header is invalid or missing');
+  }
+
+  if (!baggage || typeof baggage !== 'string' || !baggage.includes('sentry-')) {
+    throw new Error('baggage header is invalid or missing');
+  }
+
+  Sentry.captureMessage('test message');
+});

dev-packages/node-integration-tests/suites/public-api/getTracingHeadersForFetchRequest/basic-usage/test.ts

@@ -0,0 +1,17 @@
+import { afterAll, test } from 'vitest';
+import { cleanupChildProcesses, createRunner } from '../../../../utils/runner';
+
+afterAll(() => {
+  cleanupChildProcesses();
+});
+
+test('should generate tracing headers for fetch request', async () => {
+  await createRunner(__dirname, 'scenario.ts')
+    .expect({
+      event: {
+        message: 'test message',
+      },
+    })
+    .start()
+    .completed();
+});