🧪 Testing Improvement: Add edge case test for unknown routing operator

[alfieprojectsdev]

The SurveyEngine's routing logic in checkCondition defaults to false for unknown operators. While this behavior is intended, it was not explicitly tested. I have added a test case that:

1. Defines a survey with a routing rule using an unknown operator (non_existent_op).
2. Simulates an answer submission.
3. Asserts that the engine ignores the invalid rule and follows the default route.

Due to network restrictions in the environment, npx vitest run was unavailable. I verified the logic manually using a Node script with --experimental-strip-types to ensure the SurveyEngine behaves as expected.

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PR created automatically by Jules for task 10311795524156386443 started by @alfieprojectsdev

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