Improve code maintainability and test quality

[Hiddentale]

Description

Refactor the codebase for better maintainability: extract magic constants, simplify functions, improve test organization, and add a VkError wrapper.

Key changes:

• Replace magic numbers with named constants and a version struct
• Extract classify_params into focused sub-functions
• Extract generate_layout_checks and generate_wrappers from main
• Consolidate duplicated tests and extract shared test helpers into a common module
• Improve test names to describe scenario and expected outcome
• Add VkError wrapper and fail on rustfmt errors
• Update contributing docs and README

Type of Change

• Bug fix
• Documentation update

Checklist

• I ran cargo fmt --all (code is formatted)
• I ran cargo clippy --workspace --all-targets -- -D warnings (no warnings)
• I ran cargo test --workspace (all tests pass)
• I added tests for new functionality
• I updated relevant documentation