Update developer tools and code organisation

[YeeShin504]

Summary

This PR adds pre-commit hooks and moves the expensive orthogonal-completion step used by Matrix.singular_value_decomposition() into a separate worker module.

Highlights

• Added pre-commit usage guidance so contributors can run the same checks locally before committing.
• Updated contributor guidance in README.md and `CONTRIBUTING.
• Added a subprocess worker into src/ma1522/_workers.py so the orthogonal-completion step can run independently and terminated when timeout is raised.
• Added private method _get_orth(...) to that uses numerical QR fallback when symbolic Gram-Schmidt takes too long.
• Updated Matrix.singular_value_decomposition() to call the helper and expose a timeout_seconds parameter with a default of 30 seconds.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 90.83333% with 11 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/ma1522/symbolic.py	84.05%	7 Missing and 4 partials ⚠️

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