test: add unit tests for MobileErrorHandler error paths

[Dor-bl]

Added comprehensive unit test suite in test/unit/webdriver/errorhandler_test.py covering error handling edge cases in MobileErrorHandler.check_response and stack trace formatting in format_stacktrace. Coverage for appium/webdriver/errorhandler.py reached 100%.

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PR created automatically by Jules for task 6868300192386132857 started by @Dor-bl

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[Dor-bl]

Closing: duplicate of #17. Both PRs add a brand-new test/unit/webdriver/errorhandler_test.py covering format_stacktrace and MobileErrorHandler.check_response, so they conflict outright and only one can land. #17 is already open and covers this same gap (it was kept over an earlier duplicate, #18, for the same reason). This PR doesn't add coverage beyond #17 worth mirroring separately upstream.

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Generated by Claude Code

[google-labs-jules]

Closing: duplicate of #17. Both PRs add a brand-new test/unit/webdriver/errorhandler_test.py covering format_stacktrace and MobileErrorHandler.check_response, so they conflict outright and only one can land. #17 is already open and covers this same gap (it was kept over an earlier duplicate, #18, for the same reason). This PR doesn't add coverage beyond #17 worth mirroring separately upstream.

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Generated by Claude Code

Understood. Acknowledging that this work is duplicate/obsolete and stopping work on this task.