🧪 Improve testing for _rooted in process_mappings_consumption

[edithatogo]

🎯 What: The _rooted function in pic_contracts/process_mappings_consumption.py lacked explicit test coverage.
📊 Coverage: Added tests for the happy path (valid, existing file) and several error paths including non-string paths, empty strings, absolute paths, paths escaping the root directory, and non-existent files.
✨ Result: Enhanced test coverage and increased confidence in the correct handling of file paths within the contract consumption validation logic.

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PR created automatically by Jules for task 12065341565402693684 started by @edithatogo

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