Add test coverage for chatController and businessHours branches

- Add test for line 175 else branch in chatController.ts (when popup is NOT closed)
- Add test for when nextState is undefined (not in business hours)
- Add test for state reuse when hours haven't changed (object reference stability)

These tests address the coverage gaps identified in code review.

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

Author: OpenStaxClaude