profiling(node): add platform to profile_chunk envelope header

Author: JonasBa

packages/profiling-node/test/integration.test.ts

@@ -643,7 +643,9 @@ describe('ProfilingIntegration', () => {
       Sentry.profiler.stopProfiler();
       vi.advanceTimersByTime(1000);
 
-      expect(transportSpy.mock.calls?.[0]?.[0]?.[1]?.[0]?.[0]?.type).toBe('profile_chunk');
+      const envelopeHeaders = transportSpy.mock.calls?.[0]?.[0]?.[1]?.[0]?.[0];
+      expect(envelopeHeaders?.type).toBe('profile_chunk');
+      expect(envelopeHeaders?.platform).toBe('node');
     });
 
     it('sets global profile context', async () => {