-----Description-----
This task requires writing a Lean 4 function that finds the length of the longest sequence of consecutive integers present in a given list. The numbers do not need to appear in order. The elements are unique.

A consecutive sequence consists of integers that can be arranged in increasing order with no gaps. Your function should find the longest such streak.

-----Input-----
- nums: A list of integers (no duplicates).

-----Output-----
- A natural number: the length of the longest consecutive sequence.

