feat(utils): add high-speed Yul byte swapping utility

[rabsqueen]

Summary

Implements #748 by adding a high-performance Yul utility for reversing
the byte order of 256-bit words.

Changes

• Added YulByteSwapper library.
• Implemented 32-byte endian reversal using inline Yul assembly.
• Uses fixed SHR, SHL, AND, and OR operations.
• No loops or memory-buffer allocation.
• Added bytes32 and uint256 interfaces.
• Added a test harness for exercising the internal library functions.
• Added known-value, edge-case, high-level-reference, and inverse-operation tests.

Performance

The implementation performs byte reversal in constant time using
a fixed sequence of bitwise operations:

1. 8-bit group swap
2. 16-bit group swap
3. 32-bit group swap
4. 64-bit group swap
5. 128-bit half swap

There are no dynamic loops or temporary memory buffers.

Testing

Validated against:

• Known endian conversion vectors
• Zero value
• Maximum uint256
• Repeated-byte values
• High-level endian conversion reference implementation
• Double-swap/inverse property

Validation

• npm run format:check
• npm run lint
• npm run typecheck
• npm test
• npm run build
• Yul byte swapper test suite

Closes #748