The configured PIUIO or PIUBTN library path and the mapping-file lookup are separate behaviors. This distinction was unclear, making it difficult to understand what shared installations already supported and what the lookup added by PR #86 changed.
Document the per-game and shared-folder layouts, the keyboard X11 input-handler requirement, and the current search order: load the mapping beside the selected library first, then fall back to the folder containing the game's piu executable.