Kth Largest Element in a Stream

Design a class that tracks the k-th largest value in a stream of integers.

The k-th largest is the value at position k when all values seen so far are sorted from largest to smallest. Duplicates count as separate values, so in [8, 8, 3] the 2nd largest is 8.

Implement:

• KthLargest(k, nums) initializes the object with the integer k and the starting values nums (which may be empty or have fewer than k values).
• add(val) appends val to the stream and returns the k-th largest value among all values seen so far (the initial nums plus every value added).

Whenever add is called, the stream contains at least k values after val is appended, so an answer always exists.

The examples list the calls in order; the output shows each call's return value, with None for the constructor.