Modified Two Sum Problem

ClickUp task views may need to identify every distinct pair of task estimate values whose combined estimate matches a requested total. Given an integer array and a target, return all unique value pairs that sum to the target.

Each array element may be used at most once. Duplicate values in the input must not produce duplicate pairs. Within each pair, the smaller value comes first, and the result must be sorted lexicographically. Return an empty list when no valid pair exists.

Formal Specification

Implement find_unique_pairs(nums, target).

• Input: nums, a list of integers, and target, an integer.
• Output: A list of two-element integer lists. Each pair [a, b] satisfies a + b == target and represents values from two distinct input occurrences.
• The returned pairs must be unique and sorted by first value, then second value.
• Do not modify the input list.