Status: IN
`Partition.split()` divides at `len(keys)//2` (count-based median), not the lexicographic midpoint of the key range, producing equal-count halves but potentially unequal key ranges.
Source: entries/2026/05/29/range-partitioning-range_partitioning.md
mid = len(partition._data) // 2
median_key = sorted_keys[mid]
# split into [start, median) and [median, end)