Grid Teleportation Traversal

Find the minimum moves from the top-left to bottom-right in a grid with obstacles where you can move 4-directionally and, for each uppercase letter at most once, instantly teleport at zero move cost between any two cells with that letter. The core challenge is a shortest-path search (BFS) augmented by one-time zero-cost jumps per letter, so you must track/mark portal letters as consumed to avoid repeated teleports.