🧪 Add multi-level nesting test case for semantic shadowing

[Tcode-Motion]

🎯 What: Added a missing edge case test in semantic_tests.rs for the check_shadowing function in SymbolTable.
📊 Coverage: The new test test_semantic_shadowing_multiple_levels ensures that the semantic analyzer correctly detects variable shadowing across multiple levels of block scopes and accurately emits a W0010 warning, exercising the scope.iter().take(...) logic for multi-level traversal.
✨ Result: Improved test coverage and reliability for variable shadowing detection, providing a safety net for future refactoring of the semantic analyzer.

---

PR created automatically by Jules for task 15944263183734373638 started by @Tcode-Motion

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.