🧪 Add tests for extract_content in secret_scanner.py

[google-labs-jules]

🎯 What: Testing gap addressed for the extract_content function in hooks/secret_scanner.py. The function was lacking automated tests.
📊 Coverage: Scenarios for Write tool (with and without "content" key), Edit tool (with and without "new_string" key), and unhandled tool types (returning empty string) are now tested.
✨ Result: 100% test coverage for the extract_content function, improving reliability and confidence for future refactoring.

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PR created automatically by Jules for task 7057320559286808141 started by @zknpr

[google-labs-jules]

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