fix(analytics): make ctx.requestId authoritative + assert single emit

CodeRabbit findings on PR #3659:
- captureException additionalProperties construction let
  ctx.properties.requestId override ctx.requestId. Move requestId
  spread after ctx.properties so the explicit ctx.requestId wins.
- logger.posthog.transport.integration.tests.js asserted payload
  shape but not call count. Add toHaveBeenCalledTimes(1).

+1 unit test for ctx.requestId precedence.

Author: PierreBrisorgueil

lib/services/analytics.js

@@ -174,9 +174,9 @@ const captureException = (err, ctx = {}) => {
     const distinctId = ctx.distinctId || 'anonymous';
     const explicit = ctx.source ? { source: ctx.source } : {};
     const additionalProperties = {
-      requestId: ctx.requestId,
       source: 'system',
       ...(ctx.properties ?? {}),
+      ...(ctx.requestId !== undefined ? { requestId: ctx.requestId } : {}),
       ...explicit,
     };
     client.captureException(err, distinctId, additionalProperties);

lib/services/tests/analytics.captureException.unit.tests.js

@@ -108,4 +108,17 @@ describe('Analytics captureException():', () => {
       expect.objectContaining({ requestId: 'req-xyz' }),
     );
   });
+
+  test('ctx.requestId wins over ctx.properties.requestId (authoritative)', () => {
+    const err = new Error('req-precedence');
+    AnalyticsService.captureException(err, {
+      requestId: 'authoritative-req',
+      properties: { requestId: 'should-be-overridden' },
+    });
+    expect(mockPostHogInstance.captureException).toHaveBeenCalledWith(
+      err,
+      'anonymous',
+      expect.objectContaining({ requestId: 'authoritative-req' }),
+    );
+  });
 });

lib/services/tests/logger.posthog.transport.integration.tests.js

@@ -37,6 +37,7 @@ describe('logger.error → PostHog $exception (integration):', () => {
   test('logger.error(message, { error }) emits a single $exception event via SDK captureException', () => {
     const err = new Error('payment failed');
     logger.error('Charge failed for user', { error: err });
+    expect(mockPostHogInstance.captureException).toHaveBeenCalledTimes(1);
     expect(mockPostHogInstance.captureException).toHaveBeenCalledWith(
       err,
       'anonymous',