Find the Largest Number At Most X

The crane can lift at most x kilograms — pick the heaviest crate it can still handle. 🏗️

You get a SORTED list of crate weights and the limit x. Print the largest weight that is x or less, or none if even the lightest crate is too heavy.

Example:

Input: weights = [100, 250, 400, 800], x = 500 Output: 400

The boundary search finds the first weight greater than 500 (800, at position 3), so the answer sits just before it, at 400.