* std.sort.pdq: fix out-of-bounds access in partialInsertionSort

When sorting a sub-range that doesn't start at index 0, the
partialInsertionSort function could access indices below the range
start. The loop condition `while (j >= 1)` didn't respect the
arbitrary range boundaries [a, b).

This changes the condition to `while (j > a)` to ensure indices
never go below the range start, fixing the issue where pdqContext
would access out-of-bounds indices.

Fixes #25250