SetWallpaperTool
Sets the wallpaper from a local image file via WallpaperManager.setBitmap, targeting the home screen, lock screen, or both.
Requires the SET_WALLPAPER permission (normal, granted at install). The path is sandboxed to the external-storage root (canonical-path check); paths outside it are rejected. Also rejected if device policy disallows setting wallpaper (WallpaperManager.isSetWallpaperAllowed) or the image cannot be decoded.
Output keys: success, path, target, width, height.