🧪 [Add tests for error message helper]

[arvarik]

🎯 What: Added comprehensive unit tests for the getErrorMessage utility function.
📊 Coverage:

• Standard Error instances (extracts .message)
• Custom Error subclasses
• String values (returns as-is)
• Numeric values (returns string representation)
• Boolean values (returns string representation)
• null and undefined (returns "null" and "undefined")
• Plain objects (returns "[object Object]")
• Objects with custom toString() (returns the result of toString())
  ✨ Result: Increased reliability of a core utility used throughout the server for error reporting. Verified with 100% pass rate in the new test suite.

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PR created automatically by Jules for task 321854343890725033 started by @arvarik

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