Detect runs and collapse a numeric grid

You are given an m x n grid of digits (0– 9). Phase 1: Find every horizontal or vertical run of length ≥ 3 consisting of the same digit. For each run, record [row, col, length], where [row, col] is the starting cell of the run (leftmost for horizontal runs, topmost for vertical runs). Return the list of runs sorted top-to-bottom and left-to-right (row ascending, then column ascending). Phase 2: Remove all cells that belong to any such run, let numbers above fall down within each column, and fill remaining empty cells with 0. Output the resulting grid after this operation.