Return all combinations that sum to target

Given an array of **distinct positive integers** `candidates` and an integer `target`, return **all unique combinations** of `candidates` where the chosen numbers sum to `target`. Rules: - You may use each candidate **an unlimited number of times**. - Two combinations are considered the same if they contain the same multiset of numbers (order does **not** matter). - Return the combinations in any order. Example: - `candidates = [2,3,6,7]`, `target = 7` - Valid output: `[[2,2,3],[7]]` Constraints (typical): - `1 <= candidates.length <= 30` - `1 <= candidates[i] <= 200` - `1 <= target <= 500`