fix: reject all-zeroes mask when limit < Range

[asterite]

Problem Resolved

Resolves https://github.com/noir-lang/noir-library-claude/issues/10
Resolves #59

Summary of Changes

In boundary_check, if __boundary_check returned an all-zeroes array it didn't produce an assertion failure regardless of the value of limit. The fix is to replace one of the last assertions done with assert_eq(r[Range - 1], (limit < Range) as Field) which means that the last position is 0 is the limit is past the range, or 1 if it's before the range (the previous assertions make sure it's always a chain of zeroes followed by a chain of ones).

I also included tests for boundary_check as it wasn't tested, and tests for the "verify this unconstrained value" part of the function, which is now assert_boundary_mask.

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.