String Transformation Cost

You are given two strings, source and target, both consisting of lowercase English letters. Your objective is to determine the minimum number of single-character operations required to convert source into target.

You are permitted to perform the following three operations on the source string:

1. Insert: Add any single character at any position in the string.
2. Remove: Delete any single character from the string.
3. Substitute: Replace any single character with a different character.

Each operation has a uniform cost of 1. Your goal is to find the minimum total cost (i.e., the minimum number of operations) to transform source into target.

This is a classic dynamic programming problem that measures the "distance" between two strings—often referred to as the transformation distance or the minimum cost to make two strings identical through elementary edits.