The sessionId getter mints a fresh session on cold start or after a
30-min lapse, and as a side effect nulls _currentScreenName/_currentStepUid.
trackScreen() set those fields before calling the sessionId getter, so the
mint-on-cold-start side effect could immediately null the fields it had
just set, breaking the same-screen idempotency check and firing a
duplicate session_enter right after cold start.
Fix: resolve visitorId and sessionId into local variables before
assigning _currentScreenName/_currentStepUid, and use the locals in the
_enqueue() payload.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>