Improve Documentation and Standardize Project Structure

[ppant]

This submission improves the repository's documentation and organization. Key changes include:

1. Directory Refactoring: Renamed deque/ to Deque/ and Error-debug/ to ErrorHandling/ to follow the TitleCase naming convention used throughout the project.
2. Root README Enhancements:
   • Fixed all Table of Contents anchor links to correctly match GitHub's slug generation for headers with emojis (e.g., #arrays- instead of #arrays).
   • Corrected the Shell Sort complexity from $O(n \log n)$ to $O(n^2)$.
   • Updated the project structure tree and all internal links to reflect renamed directories.
3. Subdirectory Documentation:
   • Updated Deque/README.md with detailed Big O analysis for all operations (addFront/removeFront: $O(1)$, addRear/removeRear: $O(n)$ based on the list implementation).
   • Standardized ErrorHandling/README.md and removed redundant complexity notes.
4. Verification: Confirmed that all 49 non-interactive Python scripts execute successfully in the new directory structure.

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PR created automatically by Jules for task 13291672792220008858 started by @ppant

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