no_std support, infallible get/set/mask field operations

[rcgoodfellow]

This PR.

• Adds no_std support.
• Makes the mask operation infallible which bubbles up to get_field and set_field.

[Copilot]

Pull Request Overview

This PR adds no_std support to the library and makes field operations infallible by removing error handling from the mask, get_field, and set_field methods.

• Enables no_std support by replacing std imports with core and adding extern crate alloc
• Makes mask, get_field, and set_field operations infallible by removing Result return types
• Updates all call sites to use the new infallible APIs

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/src/lib.rs	Adds no_std support, converts field operations to infallible APIs, and includes mathematical proof for index safety
README.md	Updates code examples to reflect the new infallible API usage